Unable to repair items by combining them on the crafting grid

Put the summary of the bug you're having here

What I expected to happen was...:
Placing two damaged items (i.e. pickaxes) of the same type onto a crafting grid should allow you to craft another item of the same type with less damage.

What actually happened was...:
No product appeared in the crafting output slot even though both items in the crafting grid were damaged and of the same type.

Steps to Reproduce:
1. Take 2 stone pickaxes with durability approximately 40%.

2. Place them in the player's crafting grid