Khan/khan-exercises — pull request #23125 by tomyedwab (2012-06-01 23:52:53+00:00)
Title: Fixing a minor bug that would sometimes prevent the user from submitting an answer

This bug showed up in my poking around with card types. It only happens when the "completed stack" view is commented out, and I'm not sure what that has to do with the check answer button but it looks to me like the next answer button is not intended to be enabled while doing an exercise.

I think this behavior is correct.