Trying out the snapshot released today (9/28/16). In two brand new worlds, one survival and one creative, placing coal (but not charcoal) in the bottom slot of a furnace causes the game to immediately crash and produces the attached error log.

Steps to reproduce:
1. Place a furnace.
2. Open the furnace interface.
3. Place a piece of coal (not charcoal) in the bottom slot, either by right-clicking it in your inventory or clicking and moving it to the slot.
4. Game crashes.