So I've browsed the internet for about 3 hours looking for a fix, and spent another few working on it myself, but I'm stumped. I know (I think) my problem has something to do with how I've written the slots on the table, it's a 5x5, but I can't find the actual problem.

 

The NPE happens when, in game, you right click on the block.

 

Container

package blfngl.fallout.container;

import blfngl.fallout.Fallout;
import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.entity.player.InventoryPlayer;
import net.minecraft.inventory.Container;
import net.minecraft.inventory.IInventory;
import net.minecraft.inventory.InventoryCraftResult;
import net.minecraft.inventory.InventoryCrafting;
import net.minecraft.inventory.Slot;
import net.minecraft.inventory.SlotCrafting;
import net.minecraft.item.ItemStack;
import net.minecraft.world.World;

public class ContainerPowerWelder extends Container
{

public InventoryCrafting craftMatrix;
public IInventory craftResult;
private World worldObj;
private int posX;
private int posY;
private int posZ;

public ContainerPowerWelder(InventoryPlayer inventoryplayer, World world, int i, int j, int k)
{
	craftMatrix = new InventoryCrafting(this, 5, 5);
	craftResult = new InventoryCraftResult();
	worldObj = world;
	posX = i;
	posY = j;
	posZ = k;
	this.addSlotToContainer(new SlotCrafting(inventoryplayer.player, craftMatrix, craftResult, 0, 131, 36));
	System.out.println("1");
	for(int l = 0; l < 5; l++)
	{
		for(int k1 = 0; k1 < 5; k1++)
		{
			this.addSlotToContainer(new Slot(craftMatrix, k1 + l * 5, 4 + k1 * 18, 3 + l * 18));
		}

	}
	System.out.println("2");
	for(int i1 = 0; i1 < 3; i1++)
	{
		for(int l1 = 0; l1 < 9; l1++)
		{
			this.addSlotToContainer(new Slot(inventoryplayer, l1 + i1 * 9 + 9, 8 + l1 * 18, 94 + i1 * 18));
		}

	}
	System.out.println("3");
	for(int j1 = 0; j1 < 9; j1++)
	{
		this.addSlotToContainer(new Slot(inventoryplayer, j1, 8 + j1 * 18, 148));
	}

	onCraftMatrixChanged(craftMatrix);
}

public void onCraftMatrixChanged(IInventory iinventory)
{
	craftResult.setInventorySlotContents(0, PowerWelderCraftingManager.getInstance().findMatchingRecipe(craftMatrix, worldObj));
}

public void onContainerClosed(EntityPlayer entityplayer)
{
	super.onContainerClosed(entityplayer);
	if(worldObj.isRemote)
	{
		return;
	}
	for(int i = 0; i < 25; i++)
	{
		ItemStack itemstack = craftMatrix.getStackInSlot(i);
		if(itemstack != null)
		{
			entityplayer.entityDropItem(itemstack, 1.0F);
		}
	}

}

public boolean canInteractWith(EntityPlayer entityplayer)
{
	if(worldObj.getBlock(posX, posY, posZ) != Fallout.powerArmorWelder)
	{
		return false;
	} else
	{
		return entityplayer.getDistanceSq((double)posX + 0.5D, (double)posY + 0.5D, (double)posZ + 0.5D) <= 64D;
	}
}

public ItemStack transferStackInSlot(EntityPlayer par1EntityPlayer, int par2)
{
	ItemStack itemstack = null;
	Slot slot = (Slot)inventorySlots.get(par2);
	if(slot != null && slot.getHasStack())
	{
		ItemStack itemstack1 = slot.getStack();
		itemstack = itemstack1.copy();
		if(par2 == 0)
		{
			if(!mergeItemStack(itemstack1, 10, 46, true))
			{
				return null;
			}
		} else
			if(par2 >= 10 && par2 < 37)
			{
				if(!mergeItemStack(itemstack1, 37, 46, false))
				{
					return null;
				}
			} else
				if(par2 >= 37 && par2 < 46)
				{
					if(!mergeItemStack(itemstack1, 10, 37, false))
					{
						return null;
					}
				} else
					if(!mergeItemStack(itemstack1, 10, 46, false))
					{
						return null;
					}
		if(itemstack1.stackSize == 0)
		{
			slot.putStack(null);
		} else
		{
			slot.onSlotChanged();
		}
		if(itemstack1.stackSize != itemstack.stackSize)
		{
			slot.onPickupFromSlot(par1EntityPlayer, itemstack1);
		} else
		{
			return null;
		}
	}
	return itemstack;
}
}

 

 

Block

package blfngl.fallout.block;

import net.minecraft.block.Block;
import net.minecraft.block.material.Material;
import net.minecraft.creativetab.CreativeTabs;
import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.tileentity.TileEntity;
import net.minecraft.world.World;
import blfngl.fallout.Fallout;

public class BlockPowerWelder extends Block
{
public BlockPowerWelder()
{
	super(Material.ground);
	this.setCreativeTab(CreativeTabs.tabBlock);
}

@Override
public boolean onBlockActivated(World var1, int var2, int var3, int var4, EntityPlayer player, int var6, float var7, float var8, float var9)
{
	TileEntity tileEntity = var1.getTileEntity(var2, var3, var4);

	if (player.isSneaking()) // || tileEntity == null)
	{
		return false;
	}
	else
	{		
		player.openGui(Fallout.fallout, 0, var1, var2, var3, var4);
		return false;
	}		
}
}

 

 

This line causes the issues:

player.openGui(Fallout.fallout, 0, var1, var2, var3, var4);

 

Error report

---- Minecraft Crash Report ----
// Hi. I'm Minecraft, and I'm a crashaholic.

Time: 7/3/14 1:25 AM
Description: Unexpected error

java.lang.NullPointerException: Unexpected error
at cpw.mods.fml.common.network.NetworkRegistry.getLocalGuiContainer(NetworkRegistry.java:263)
at cpw.mods.fml.common.network.internal.FMLNetworkHandler.openGui(FMLNetworkHandler.java:93)
at net.minecraft.entity.player.EntityPlayer.openGui(EntityPlayer.java:2515)
at blfngl.fallout.block.BlockPowerWelder.onBlockActivated(BlockPowerWelder.java:30)
at net.minecraft.client.multiplayer.PlayerControllerMP.onPlayerRightClick(PlayerControllerMP.java:380)
at net.minecraft.client.Minecraft.func_147121_ag(Minecraft.java:1499)
at net.minecraft.client.Minecraft.runTick(Minecraft.java:2012)
at net.minecraft.client.Minecraft.runGameLoop(Minecraft.java:997)
at net.minecraft.client.Minecraft.run(Minecraft.java:912)
at net.minecraft.client.main.Main.main(Main.java:112)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:134)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Stacktrace:
at cpw.mods.fml.common.network.NetworkRegistry.getLocalGuiContainer(NetworkRegistry.java:263)
at cpw.mods.fml.common.network.internal.FMLNetworkHandler.openGui(FMLNetworkHandler.java:93)
at net.minecraft.entity.player.EntityPlayer.openGui(EntityPlayer.java:2515)
at blfngl.fallout.block.BlockPowerWelder.onBlockActivated(BlockPowerWelder.java:30)
at net.minecraft.client.multiplayer.PlayerControllerMP.onPlayerRightClick(PlayerControllerMP.java:380)
at net.minecraft.client.Minecraft.func_147121_ag(Minecraft.java:1499)

-- Affected level --
Details:
Level name: MpServer
All players: 1 total; [EntityClientPlayerMP['Player988'/366, l='MpServer', x=204.50, y=74.62, z=193.50]]
Chunk stats: MultiplayerChunkCache: 225, 225
Level seed: 0
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options: 
Level spawn location: World: (208,64,192), Chunk: (at 0,4,0 in 13,12; contains blocks 208,0,192 to 223,255,207), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 217753 game time, 38699 day time
Level dimension: 0
Level storage version: 0x00000 - Unknown?
Level weather: Rain time: 0 (now: true), thunder time: 0 (now: false)
Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: false
Forced entities: 118 total; [EntityCreeper['Creeper'/273, l='MpServer', x=286.16, y=64.00, z=237.00], EntityCreeper['Creeper'/272, l='MpServer', x=275.75, y=35.00, z=224.94], EntityWitch['Witch'/258, l='MpServer', x=279.50, y=70.00, z=167.50], EntityChicken['Chicken'/256, l='MpServer', x=269.76, y=66.02, z=127.40], EntityBat['Bat'/257, l='MpServer', x=281.56, y=37.23, z=158.45], EntityCreeper['Creeper'/262, l='MpServer', x=278.72, y=22.00, z=207.72], EntityCreeper['Creeper'/263, l='MpServer', x=280.58, y=22.00, z=211.72], EntityZombie['Zombie'/260, l='MpServer', x=284.88, y=31.00, z=197.53], EntityChicken['Chicken'/261, l='MpServer', x=283.47, y=64.00, z=204.53], EntityCreeper['Creeper'/266, l='MpServer', x=282.00, y=22.00, z=210.63], EntityBat['Bat'/267, l='MpServer', x=281.63, y=22.73, z=211.60], EntityCreeper['Creeper'/264, l='MpServer', x=281.00, y=22.00, z=210.94], EntityCreeper['Creeper'/265, l='MpServer', x=281.50, y=22.00, z=214.50], EntityBat['Bat'/270, l='MpServer', x=274.44, y=38.70, z=216.30], EntitySkeleton['Skeleton'/271, l='MpServer', x=276.31, y=36.00, z=229.47], EntityBat['Bat'/268, l='MpServer', x=275.50, y=22.82, z=206.72], EntityZombie['Zombie'/269, l='MpServer', x=279.44, y=35.00, z=220.00], EntityCreeper['Creeper'/76, l='MpServer', x=125.56, y=56.00, z=155.00], EntityCreeper['Creeper'/78, l='MpServer', x=126.50, y=47.00, z=238.50], EntityCreeper['Creeper'/80, l='MpServer', x=126.41, y=23.00, z=244.22], EntityZombie['Zombie'/93, l='MpServer', x=136.69, y=57.00, z=157.50], EntityZombie['Zombie'/92, l='MpServer', x=135.63, y=57.00, z=157.50], EntityChicken['Chicken'/95, l='MpServer', x=131.63, y=56.00, z=152.56], EntityZombie['Zombie'/94, l='MpServer', x=135.38, y=63.00, z=146.50], EntitySquid['Squid'/88, l='MpServer', x=141.40, y=59.26, z=137.19], EntityZombie['Zombie'/102, l='MpServer', x=142.56, y=28.00, z=192.78], EntitySkeleton['Skeleton'/103, l='MpServer', x=141.55, y=38.00, z=252.70], EntityZombie['Zombie'/100, l='MpServer', x=142.34, y=29.00, z=187.94], EntityBat['Bat'/101, l='MpServer', x=133.00, y=28.58, z=205.38], EntityZombie['Zombie'/98, l='MpServer', x=137.16, y=45.00, z=167.44], EntityCreeper['Creeper'/99, l='MpServer', x=138.97, y=22.00, z=179.50], EntitySkeleton['Skeleton'/96, l='MpServer', x=132.44, y=18.00, z=160.06], EntityZombie['Zombie'/97, l='MpServer', x=136.31, y=45.00, z=167.66], EntityChicken['Chicken'/104, l='MpServer', x=133.59, y=64.00, z=250.59], EntityChicken['Chicken'/105, l='MpServer', x=136.63, y=64.00, z=267.59], EntitySquid['Squid'/119, l='MpServer', x=148.33, y=59.00, z=140.04], EntitySquid['Squid'/118, l='MpServer', x=149.18, y=59.38, z=141.63], EntitySquid['Squid'/117, l='MpServer', x=149.32, y=59.00, z=142.74], EntitySquid['Squid'/116, l='MpServer', x=147.53, y=59.32, z=142.13], EntitySquid['Squid'/127, l='MpServer', x=156.89, y=59.13, z=146.50], EntityItem['item.item.dyePowder.black'/126, l='MpServer', x=158.13, y=48.13, z=155.88], EntityItem['item.item.dyePowder.black'/125, l='MpServer', x=152.33, y=29.13, z=147.86], EntityItem['item.item.dyePowder.black'/124, l='MpServer', x=154.91, y=34.13, z=148.13], EntityClientPlayerMP['Player988'/366, l='MpServer', x=204.50, y=74.62, z=193.50], EntityCreeper['Creeper'/123, l='MpServer', x=149.50, y=20.00, z=153.50], EntityCreeper['Creeper'/122, l='MpServer', x=152.50, y=18.00, z=151.41], EntitySkeleton['Skeleton'/121, l='MpServer', x=147.94, y=18.00, z=145.53], EntityZombie['Zombie'/120, l='MpServer', x=157.41, y=14.00, z=155.75], EntitySquid['Squid'/141, l='MpServer', x=159.07, y=57.00, z=139.50], EntityChicken['Chicken'/143, l='MpServer', x=172.82, y=62.27, z=144.53], EntityBat['Bat'/142, l='MpServer', x=157.46, y=16.89, z=150.35], EntityBat['Bat'/129, l='MpServer', x=147.63, y=38.10, z=172.38], EntitySquid['Squid'/128, l='MpServer', x=154.50, y=59.42, z=145.50], EntitySkeleton['Skeleton'/131, l='MpServer', x=150.91, y=13.00, z=179.50], EntitySkeleton['Skeleton'/130, l='MpServer', x=158.59, y=69.00, z=175.94], EntityZombie['Zombie'/133, l='MpServer', x=158.38, y=72.00, z=192.53], EntityZombie['Zombie'/132, l='MpServer', x=147.50, y=26.00, z=186.94], EntityChicken['Chicken'/135, l='MpServer', x=155.41, y=63.00, z=255.47], EntityChicken['Chicken'/134, l='MpServer', x=149.56, y=63.00, z=250.47], EntityChicken['Chicken'/152, l='MpServer', x=178.67, y=72.00, z=172.33], EntityChicken['Chicken'/153, l='MpServer', x=178.44, y=71.00, z=227.47], EntitySkeleton['Skeleton'/154, l='MpServer', x=184.50, y=98.00, z=244.88], EntitySkeleton['Skeleton'/155, l='MpServer', x=183.63, y=98.00, z=247.03], EntityCreeper['Creeper'/156, l='MpServer', x=176.56, y=52.00, z=258.75], EntityCreeper['Creeper'/157, l='MpServer', x=176.34, y=52.00, z=261.09], EntityItem['item.item.dyePowder.black'/144, l='MpServer', x=165.88, y=48.13, z=154.88], EntityZombie['Zombie'/145, l='MpServer', x=165.56, y=23.00, z=252.00], EntityChicken['Chicken'/146, l='MpServer', x=164.47, y=71.00, z=249.66], EntityChicken['Chicken'/151, l='MpServer', x=176.41, y=67.00, z=136.66], EntityChicken['Chicken'/165, l='MpServer', x=202.20, y=78.00, z=266.21], EntityChicken['Chicken'/182, l='MpServer', x=213.59, y=73.00, z=205.41], EntitySkeleton['Skeleton'/181, l='MpServer', x=212.98, y=19.00, z=117.44], EntityChicken['Chicken'/204, l='MpServer', x=225.53, y=72.00, z=257.44], EntityCreeper['Creeper'/201, l='MpServer', x=228.53, y=33.00, z=262.56], EntityBat['Bat'/200, l='MpServer', x=239.38, y=38.10, z=268.34], EntityCreeper['Creeper'/203, l='MpServer', x=227.50, y=41.00, z=262.75], EntityCreeper['Creeper'/202, l='MpServer', x=226.84, y=41.00, z=264.09], EntityBat['Bat'/197, l='MpServer', x=227.65, y=33.92, z=231.66], EntityBat['Bat'/196, l='MpServer', x=228.75, y=35.10, z=222.75], EntityChicken['Chicken'/199, l='MpServer', x=233.44, y=75.00, z=251.44], EntityMinecartChest['entity.MinecartChest.name'/198, l='MpServer', x=236.50, y=41.50, z=255.50], EntityBat['Bat'/193, l='MpServer', x=225.25, y=11.33, z=170.33], EntitySkeleton['Skeleton'/195, l='MpServer', x=234.31, y=20.00, z=216.53], EntitySkeleton['Skeleton'/194, l='MpServer', x=235.69, y=24.00, z=163.75], EntityZombie['Zombie'/223, l='MpServer', x=257.50, y=13.00, z=120.34], EntityChicken['Chicken'/216, l='MpServer', x=254.47, y=65.00, z=195.53], EntityMinecartChest['entity.MinecartChest.name'/217, l='MpServer', x=255.50, y=36.50, z=237.50], EntityChicken['Chicken'/218, l='MpServer', x=245.53, y=70.00, z=224.59], EntityChicken['Chicken'/219, l='MpServer', x=241.60, y=78.00, z=224.47], EntityZombie['Zombie'/212, l='MpServer', x=251.75, y=11.00, z=139.53], EntityZombie['Zombie'/213, l='MpServer', x=247.47, y=33.00, z=131.03], EntityBat['Bat'/214, l='MpServer', x=256.26, y=12.54, z=142.38], EntityCreeper['Creeper'/215, l='MpServer', x=249.64, y=60.00, z=205.78], EntityZombie['Zombie'/211, l='MpServer', x=247.41, y=12.00, z=118.56], EntityZombie['Zombie'/239, l='MpServer', x=267.63, y=38.00, z=214.47], EntityZombie['Zombie'/238, l='MpServer', x=271.72, y=49.00, z=194.44], EntityBat['Bat'/237, l='MpServer', x=276.76, y=23.04, z=207.66], EntitySkeleton['Skeleton'/236, l='MpServer', x=264.88, y=18.00, z=192.47], EntityCreeper['Creeper'/235, l='MpServer', x=268.53, y=22.00, z=207.03], EntityChicken['Chicken'/234, l='MpServer', x=264.81, y=62.62, z=188.56], EntityChicken['Chicken'/233, l='MpServer', x=258.44, y=71.00, z=147.56], EntityChicken['Chicken'/232, l='MpServer', x=261.59, y=71.00, z=146.53], EntityChicken['Chicken'/231, l='MpServer', x=258.41, y=70.00, z=124.68], EntitySkeleton['Skeleton'/230, l='MpServer', x=269.50, y=34.00, z=128.88], EntitySkeleton['Skeleton'/229, l='MpServer', x=275.13, y=33.00, z=128.53], EntityZombie['Zombie'/228, l='MpServer', x=261.34, y=19.00, z=131.03], EntitySkeleton['Skeleton'/227, l='MpServer', x=271.50, y=30.00, z=133.84], EntityBat['Bat'/226, l='MpServer', x=271.29, y=12.20, z=124.44], EntityChicken['Chicken'/225, l='MpServer', x=270.53, y=65.00, z=126.81], EntityZombie['Zombie'/224, l='MpServer', x=271.38, y=30.00, z=117.06], EntityChicken['Chicken'/255, l='MpServer', x=277.06, y=64.41, z=133.22], EntityBat['Bat'/252, l='MpServer', x=274.75, y=5.10, z=133.22], EntityZombie['Zombie'/253, l='MpServer', x=282.94, y=19.00, z=142.50], EntityChicken['Chicken'/251, l='MpServer', x=277.44, y=64.00, z=120.47], EntityZombie['Zombie'/249, l='MpServer', x=275.30, y=3.00, z=127.70], EntitySkeleton['Skeleton'/242, l='MpServer', x=257.50, y=46.00, z=241.69], EntitySkeleton['Skeleton'/240, l='MpServer', x=262.94, y=56.00, z=213.53], EntityChicken['Chicken'/241, l='MpServer', x=267.72, y=67.00, z=232.22]]
Retry entities: 0 total; []
Server brand: fml,forge
Server type: Integrated singleplayer server
Stacktrace:
at net.minecraft.client.multiplayer.WorldClient.addWorldInfoToCrashReport(WorldClient.java:412)
at net.minecraft.client.Minecraft.addGraphicsAndWorldToCrashReport(Minecraft.java:2524)
at net.minecraft.client.Minecraft.run(Minecraft.java:941)
at net.minecraft.client.main.Main.main(Main.java:112)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:134)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

-- System Details --
Details:
Minecraft Version: 1.7.2
Operating System: Windows 7 (amd64) version 6.1
Java Version: 1.7.0_60, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 862782072 bytes (822 MB) / 1056309248 bytes (1007 MB) up to 1056309248 bytes (1007 MB)
JVM Flags: 3 total; -Xincgc -Xmx1024M -Xms1024M
AABB Pool Size: 9779 (547624 bytes; 0 MB) allocated, 2 (112 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
FML: MCP v9.03 FML v7.2.211.1121 Minecraft Forge 10.12.2.1121 5 mods loaded, 5 mods active
mcp{9.03} [Minecraft Coder Pack] (minecraft.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
FML{7.2.211.1121} [Forge Mod Loader] (forgeSrc-1.7.2-10.12.2.1121.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Forge{10.12.2.1121} [Minecraft Forge] (forgeSrc-1.7.2-10.12.2.1121.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
PlayerAPI{1.4} [Player API] (minecraft.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
fallout{v0.3} [The Fallout Mod] (bin) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Launched Version: 1.6
LWJGL: 2.9.0
OpenGL: AMD Radeon(TM) HD 6480G GL version 4.1.10600 Compatibility Profile Context, ATI Technologies Inc.
Is Modded: Definitely; Client brand changed to 'fml,forge'
Type: Client (map_client.txt)
Resource Packs: []
Current Language: English (US)
Profiler Position: N/A (disabled)
Vec3 Pool Size: 3319 (185864 bytes; 0 MB) allocated, 16 (896 bytes; 0 MB) used
Anisotropic Filtering: Off (1)

 

Thanks