Reproduced easily in both snapshots. I did the following:
1. Open game.
2. Open chest.
3. Press E and 2 simultaneously.
4. Observe crash.
I've since found that other keys also cause the crash. I'll edit those into the OP.
I will try to reproduce in 14w18b, but first I will try to reproduce in 14w17a just to make sure I can do it again at all.
What is it?
If this is a feature, what's the point of it?
I found it pretty easy to reproduce. Check out my report (MC-54685, listed as a duplicate here) for details.
Edit: OP's edited it in.