Wizard Step 5: Error Message "speakers call data can't be after the event start date" even though call date is before event

[mariobehling]

When an organizer plays around with the call date and chooses the wrong date an error message appears. When the organizers fixes it the error message still appears "speakers call data can't be after the event start date". Sometimes the error message does not appear even if the dates for "Call for Speakers" are after the event.

Compare: http://eventyay.com/events/e96320f3/edit/sessions-speakers