When I go to melt ore in my furnace, it won't let me choose what to burn.

Put the summary of the bug you're having here

What I expected to happen was
I would go to my furnace to melt gold ore and use coal to melt it.
What actually happened was...:
I selected gold ore, but when I tried to select what to burn it wouldn't let me.

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...
3. ...