[Demonstration 1]

[Buggy Method]
@Override
public boolean isItemValid(ItemStack itemStack) {
    return itemStack.getItem().getUnlocalizedName().equals("item.enderPearl");
}

[Buggy Hunk]
return itemStack.getItem().getUnlocalizedName().equals("item.enderPearl");

[Patch]
return itemStack != null && itemStack.getItem().getUnlocalizedName().equals("item.enderPearl");

[Demonstration 2]

[Buggy Method]
@Override
public List<ItemStack> getDrops(IBlockAccess world, BlockPos pos, IBlockState state, int fortune) {
    TileEntityBase tileEntityBase = TileHelper.getTileEntity(world, pos, TileEntityBase.class);
    if (tileEntityBase != null) {
        final ItemStack itemStack = new ItemStack(this);
        NBTTagCompound machineItemData = tileEntityBase.getMachineItemData();
        if (machineItemData != null) {
            NBTTagCompound itemTag = new NBTTagCompound();
            itemTag.setTag("MachineItemData", machineItemData);
            itemStack.setTagCompound(itemTag);
        }
        if (tileEntityBase.hasCustomName()) {
            itemStack.setStackDisplayName(tileEntityBase.getCustomName());
        }
        ArrayList<ItemStack> drops = new ArrayList<ItemStack>();
        drops.add(itemStack);
        return drops;
    }
    return super.getDrops(world, pos, state, fortune);
}

[Buggy Hunk]
final ItemStack itemStack = new ItemStack(this);

[Patch]
final ItemStack itemStack = new ItemStack(this, 1, tileEntityBase.getBlockMetadata());

[Demonstration 3]

[Buggy Method]
public void updateTicker() {
    xPos++;
    if (xPos > scroll[0].length())
        xPos = 0;
    for (int n = 0; n < 9 * 6; n++) {
        super.putStackInSlot(n, null);
    }
    for (int y = 0; y < 5; y++) {
        for (int x = 0; x < 9; x++) {
            String rowString = scroll[y];
            if (xPos + x < rowString.length() && rowString.charAt(xPos + x) == '1')
                super.putStackInSlot(x + (y * 9), new ItemStack(redstoneBlock));
            //else putStackInSlot(x + (y * 9), new ItemStack(slimeball));
        }
    }
}

[Buggy Hunk]
super.putStackInSlot(n, null);

[Patch]
super.putStackInSlot(n, ItemStack.NULL_STACK);