Ticking Entity for Chest in Minecart caused Superflat Minecraft world to crash

I had a chest in a minecart that was already rolling when I opened my saved game of a superflat world that I created to mess around with all the new toys the 1.5 update came with.

I had the cart going around in a circle with one powered rail to push it along. I noticed it wasn't making any noise, so I wandered over to check it out. I was just about to jump up on the rails to stop it when the error message popped up.