Put the summary of the bug you're having here

What I expected to happen was...:
that I could tap on the fuel slot to insert coal.

What actually happened was....•
it didn't go to the fuel slot, instead it stayed on the smelting slot.

Steps to Reproduce:
1. First I tapped on the furnace as usual
2. then I needed to put in some fuel because there was none
3. but it wouldn't go into the fuel slot
4. after that I decided to take out the to-be-smelted item but it wouldn't come back into my inventory
5. so I had to break the furnace.