Quick preview should probably not fall back to trying to save the question

[jpslav]

Right now, if you have logic in your question (with errors), and hit quick preview (before having saved), it executes an HTML update (non remote, non JS) taking you to a page that talks about the errors and then you can't get back to your draft problem (you can get back there but the text is blank).

[Dantemss]

Maybe we want to keep doing preview like we are now, but show the error using JS so the user doesn't lose anything?