[1.7.2] Shift Clicking In Custom Workbench Creates Ghost Items [SOLVED]

package com.gamc.naturalupgrades.table;

import com.gamc.naturalupgrades.NaturalUpgrades;

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 ContainerUpgradeTable extends Container {

// Notes for important slots and their locations
final int INPUT_1 = 0, INPUT_2 = 1, INPUT_3 = 2, INPUT_4 = 3, OUTPUT = 4;
final int INV_START = 5, INV_END = 31, HOTBAR_START = 32, HOTBAR_END = 40;

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

public ContainerUpgradeTable(InventoryPlayer invPlayer, World world, int x, int y, int z){
	craftMatrix = new InventoryCrafting(this, 2, 2);
	craftResult = new InventoryCraftResult();
	worldObj = world;
	posX = x;
	posY = y;
	posZ = z;

	// Slots where you put the items to make the end result
	this.addSlotToContainer(new Slot(this.craftMatrix, INPUT_1, 44 + 0 * 18, 22 + 0 * 18));
	this.addSlotToContainer(new Slot(this.craftMatrix, INPUT_2, 62 + 0 * 18, 22 + 1 * 18));
	this.addSlotToContainer(new Slot(this.craftMatrix, INPUT_3, 44 + 0 * 18, 22 + 2 * 18));
	this.addSlotToContainer(new Slot(this.craftMatrix, INPUT_4, 26 + 0 * 18, -14 + 3 * 18));
	// Slot where the end result of the recipe goes
	this.addSlotToContainer(new SlotCrafting(invPlayer.player, craftMatrix, craftResult, OUTPUT, 116, 39));
	// Slots for player inventory
	for (int i = 0; i < 3; i++) {
		for (int j = 0; j < 9; ++j) {
		this.addSlotToContainer(new Slot(invPlayer, j + i * 9 + 9, 8 + j * 18, 96 + i * 18));
		}
	}
	// Slots for player hotbar
	for (int i = 0; i < 9; i++) {
		this.addSlotToContainer(new Slot(invPlayer, i, 8 + i * 18, 154));
	}
	onCraftMatrixChanged(craftMatrix);
}
@Override
public void onContainerClosed(EntityPlayer par1EntityPlayer)
    {
        super.onContainerClosed(par1EntityPlayer);
        
        if (!this.worldObj.isRemote)
        {
            for (int i = 0; i < 4; ++i)
            {
                ItemStack itemstack = this.craftMatrix.getStackInSlotOnClosing(i);
                
                if (itemstack != null)
                {
                    par1EntityPlayer.dropPlayerItemWithRandomChoice(itemstack, false);
                }
                
            }
        }
    }

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

@Override
public boolean canInteractWith(EntityPlayer player) {
	if(worldObj.getBlock(posX, posY, posZ) != NaturalUpgrades.upgradeTable){
		return true;
	}else{
		return player.getDistanceSq((double)posX + 0.5D, (double)posY + 0.5D, (double)posZ + 0.5D) <= 64.0D;
	}
}

// Set shift-clicking for this container and ensure the game doesn't crash when trying to do so
    public ItemStack transferStackInSlot(EntityPlayer par1EntityPlayer, int parSlot)
    {
    	// Prepare the itemstack
    	ItemStack itemstack = null;
    	// Save the slot you clicked
        Slot slot = (Slot)this.inventorySlots.get(parSlot);
        // Make sure the slot you clicked actually has something there
        if (slot != null && slot.getHasStack())
        {
        	// Set the itemstack
            ItemStack itemstack1 = slot.getStack();
            // Make a copy of the itemstack
            itemstack = itemstack1.copy();

            // Check if the shift click occurred in the output slot
            if (parSlot == OUTPUT)
            {
            	// Try to move the clicked item to somewhere starting on the hotbar
                if (!this.mergeItemStack(itemstack1, INV_START, HOTBAR_END + 1, true))
                {
                	// Give up on life and stop here
                    return null;
                }
                // If itemstack has more items than itemstack1, look for a different itemstack
                slot.onSlotChange(itemstack1, itemstack);
            }
            // Was the click anywhere outside of the inventory slots?
            else if (parSlot >= INV_START && parSlot < INV_END)
            {
            	// Try to move the clicked item into the hotbar
                if (!this.mergeItemStack(itemstack1, HOTBAR_START, HOTBAR_END, false))
                {
                	// Give up on life and stop here
                    return null;
                }
            }
            // Was the click anywhere outside of the hotbar slots?
            else if (parSlot >= HOTBAR_START && parSlot < HOTBAR_END)
            {
            	// Try to move the clicked item into the inventory
                if (!this.mergeItemStack(itemstack1, INV_START, INV_END, false))
                {
                	// Give up on life and stop here
                    return null;
                }
            }
            // Try to move the item anywhere possible in the player's inventory
            else if (!this.mergeItemStack(itemstack1, INV_START, HOTBAR_END, false))
            {
            	// Give up on life and stop here
                return null;
            }
            // If itemstack1's stacksize is the same as output put a null stack
            if (itemstack1.stackSize == OUTPUT)
            {
            	// Put a null stack
                slot.putStack((ItemStack)null);
            }
            else
            {
            	// Let the game know the slot has changed
                slot.onSlotChanged();
            }
            // Check if the two itemstacks' sizes are equal
            if (itemstack1.stackSize == itemstack.stackSize)
            {
            	// Give up on life and stop here
                return null;
            }
         	// Let the game know the slot has changed
            slot.onPickupFromSlot(par1EntityPlayer, itemstack1);
        }
        // Success?
        return itemstack;
    }
}