Before this patch, changing a problem from anything to a multiple choice question would cause failures since the most recent submissions would indicate that all past submissions should contain monikers, when in fact they won't. The answer distribution output for this scenario will definitely be wierd, but all bets are off when you modify a problem like this.

Change-Id: Ib72439c37fbe178f2320f7c48cc8bbd687ed7f02