The game crashed when you smelting in furnace minecraft snapshot 1.11
When i was mining in cave and trying to smelt irons, the game crashed !
I restarted game about 3 times and same things happened !
So i try put a coal into the furnace, game crashed. And then i try other version ( include 1.10 ) i put coal in, it work still fine.
This bug has already been fixed, see MC-107392. Also please search before creating a bug report to see if the bug has been reported already.