In 1.11 the cardboard box tooltip always shows "Air" as it's block content.

How to reproduce:

1. Give yourself a cardboard box
2. Pack an item (example obsidian)
3. Break it in survival
4. Look at tooltip
5. Place and unpack item
6. Original item is in the world

Expected output:
Show correct block name on the tooltip.

Possible solution:
Currently there's a ItemStack being made (L57 of ItemBlockCardboardBox) with block id and meta as arguments. But the constructor of itemstack with accepts block and an int as argument, uses the int as amount.
Changing it to ItemStack(Block blockIn, int amount, int meta) should solve this issue. Thus adding an extra amount argument which is larger than 0, resulting in a valid ItemStack.

Fixed in dev!