Furnaces in Minecarts won't open.

Put the summary of the bug you're having here
I expected for the furnace to open. Furnace in minecart did not open.
What I expected to happen was...:
Describe what you thought should happen here
I thought the furnace in the minecart was supposed to open.
What actually happened was...:
Describe what happened here
What happened was that the furnace in the minecart did not open.
Steps to Reproduce:
1. Go into survival singleplayer.
2. Make a furnace and minecart, and make it into a Furnace Minecart.
3. Lastly, try to open the furnace. (By the way, in 1.7.2)