Fix errors when manipulating the "New Review Request" field in wonky ways.
Review Request #3529 — Created Nov. 17, 2012 and submitted
Fix errors when manipulating the "New Review Request" field in wonky ways. On the "New Review Request" form, if the user first chooses a perforce repository and enters a change number, but then changes the repository type to "None (Graphics Only)", the changenum field will still be sent to the server. Unfortunately, NewReviewRequestForm.create() was conditionalizing only on "changenum" and nothing else.