I don't even know what's causing this one. It happens whenever I right click an item that I created.

 

Note: It works perfectly the first two times I use it but on the third one it crashes. Also this only seems to pertain to the Skin type.

 

Error

14:22:29] [server thread/FATAL] [FML]: Exception caught executing FutureTask: java.util.concurrent.ExecutionException: java.lang.NullPointerException
java.util.concurrent.ExecutionException: java.lang.NullPointerException
at java.util.concurrent.FutureTask.report(Unknown Source) ~[?:1.7.0_79]
at java.util.concurrent.FutureTask.get(Unknown Source) ~[?:1.7.0_79]
at net.minecraftforge.fml.common.FMLCommonHandler.callFuture(FMLCommonHandler.java:715) [FMLCommonHandler.class:?]
at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:727) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:669) [MinecraftServer.class:?]
at net.minecraft.server.integrated.IntegratedServer.tick(IntegratedServer.java:171) [integratedServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:540) [MinecraftServer.class:?]
at java.lang.Thread.run(Unknown Source) [?:1.7.0_79]
Caused by: java.lang.NullPointerException
at net.minecraft.server.management.ItemInWorldManager.tryUseItem(ItemInWorldManager.java:398) ~[itemInWorldManager.class:?]
at net.minecraft.network.NetHandlerPlayServer.processPlayerBlockPlacement(NetHandlerPlayServer.java:607) ~[NetHandlerPlayServer.class:?]
at net.minecraft.network.play.client.C08PacketPlayerBlockPlacement.processPacket(C08PacketPlayerBlockPlacement.java:67) ~[C08PacketPlayerBlockPlacement.class:?]
at net.minecraft.network.play.client.C08PacketPlayerBlockPlacement.processPacket(C08PacketPlayerBlockPlacement.java:114) ~[C08PacketPlayerBlockPlacement.class:?]
at net.minecraft.network.PacketThreadUtil$1.run(PacketThreadUtil.java:24) ~[PacketThreadUtil$1.class:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) ~[?:1.7.0_79]
at java.util.concurrent.FutureTask.run(Unknown Source) ~[?:1.7.0_79]
at net.minecraftforge.fml.common.FMLCommonHandler.callFuture(FMLCommonHandler.java:714) ~[FMLCommonHandler.class:?]

 

Item Class

@Override
public ItemStack onItemRightClick(ItemStack itemStackIn, World worldIn, EntityPlayer playerIn){
	if (!worldIn.isRemote){
		if(!playerIn.capabilities.isCreativeMode){
			if(PackManager.crackPack(playerIn, type)){
				itemStackIn.stackSize --;
				return null;
			}else{
				playerIn.addChatMessage(new ChatComponentText(EnumChatFormatting.RED + "You are out of inventory space!"));
			}
		}else{
			playerIn.addChatMessage(new ChatComponentText(EnumChatFormatting.RED + "You must be in survival mode to use this!"));
		}
	}
	return itemStackIn;
}

 

More code that might be helpful.

/**
 * Opens a trail pack for the player.
 * @param player
 */
public static boolean crackPack(EntityPlayer player, EnumPackType type){
	if(!player.worldObj.isRemote){
		switch(type){
		default:
			logger.error("Invalid pack type for type " + type + "!");
			return false;
		case Trail:
			if(player.inventory.hasItem(ItemManager.trailPack)){
				Trail trail = TrailManager.getRandomTrail();

				ItemStack is = new ItemStack(ItemManager.openedTrailPack, 1);
				NBTTagCompound tag = new NBTTagCompound();
				is.setTagCompound(tag);
				tag.setString("Type", EnumPackType.Trail.toString());
				tag.setString("Trail", trail.getName());
				is.setStackDisplayName("" + EnumAppRarity.getColorFromTrail(trail) + trail.getRarity() + EnumChatFormatting.AQUA + " Trail Pack");

				if(player.inventory.addItemStackToInventory(is)){
					player.addChatMessage(new ChatComponentText(EnumChatFormatting.AQUA + "You have cracked a " + EnumAppRarity.getColorFromTrail(trail) + trail.getRarity() + EnumChatFormatting.AQUA + " Trail of " + EnumAppRarity.getColorFromTrail(trail) + trail.getName() + "!"));
					if(trail.getRarity() == EnumAppRarity.Mythic){
						PacketManager.sendPacketToAll(new PacketChatMessage(EnumChatFormatting.GOLD + player.getName() + " just cracked a " + EnumAppRarity.getColorFromTrail(trail) + trail.getRarity() + EnumChatFormatting.GOLD + " Trail of " + EnumAppRarity.getColorFromTrail(trail) + trail.getName() + "!"));
					}
					return true;
				}else{
					return false;
				}
			}
			break;
		case Skin:
			if(player.inventory.hasItem(ItemManager.skinPack)){
				Skin skin = SkinManager.getRandomSkin();

				ItemStack is = new ItemStack(ItemManager.openedSkinPack, 1);
				NBTTagCompound tag = new NBTTagCompound();
				is.setTagCompound(tag);
				tag.setString("Type", EnumPackType.Skin.toString());
				tag.setString("Skin", skin.getName());
				is.setStackDisplayName("" + EnumAppRarity.getColorFromRarity(skin.getRarity()) + skin.getRarity() + EnumChatFormatting.AQUA + " Skin Pack");

				if(player.inventory.addItemStackToInventory(is)){
					player.addChatMessage(new ChatComponentText(EnumChatFormatting.AQUA + "You have cracked a " + EnumAppRarity.getColorFromRarity(skin.getRarity()) + skin.getRarity() + EnumChatFormatting.AQUA + " Skin of " + EnumAppRarity.getColorFromRarity(skin.getRarity()) + skin.getName() + "!"));
					if(skin.getRarity() == EnumAppRarity.Mythic){
						PacketManager.sendPacketToAll(new PacketChatMessage(EnumChatFormatting.GOLD + player.getName() + " just cracked a " + EnumAppRarity.getColorFromRarity(skin.getRarity()) + skin.getRarity() + EnumChatFormatting.GOLD + " Skin of " + EnumAppRarity.getColorFromRarity(skin.getRarity()) + skin.getName() + "!"));
					}
					return true;
				}else{
					return false;
				}
			}
			break;
		}

	}
	return false;
}

I think the error is caused by returning null from

Item#onItemRightClick

.

ItemInWorldManager#tryUseItem

expects a non-null

ItemStack

to be returned, even if its

stackSize

is 0 (which it explicitly checks for).

 

Oddly enough, it does check if the returned

ItemStack

is null; but only after checking that the returned

ItemStack

is equal to the original

ItemStack

(which can't possibly be null at that point).

I think the error is caused by returning null from

Item#onItemRightClick

.

ItemInWorldManager#tryUseItem

expects a non-null

ItemStack

to be returned, even if its

stackSize

is 0 (which it explicitly checks for).

 

Oddly enough, it does check if the returned

ItemStack

is null; but only after checking that the returned

ItemStack

is equal to the original

ItemStack

(which can't possibly be null at that point).

 

If I don't return null then for whatever ungodly reason is it starts to give me negative item stack sizes.

 

EDIT: Just for testing purposes I made it return the itemstack regardless but the error is still happening.

EDIT EDIT: Well I take back my last edit, I see your reasoning so I made it return the itemstack and now it crashes without any errors.

Okay i've solved the last issue. Turns out I had an unbroken while loop. Thanks for the help, I can't believe that bug didn't show up until now.