InstructorFeedbackResultsPage: '14 Feb 1970, 00:00' was changed to 'unspecified (to be published manually)' #2626

Fixes #2626
Sorry, there is a piece of info that I didn't mention earlier that is causing the confusion. We don't have a database field to store the 'publish manually' and 'immediately' options. Instead, we store that information in the 'visible from' field using special dates. 14 Feb 1970, 00:00 means 'immediately' (not 'publish manually' as I said originally). There is another special date we used to indicate 'publish manually' `(Const.TIME_REPRESENTS_LATER)`. When the session is published, the date is changed to the actual time it was published.  
The problem we are trying to fix is, the special date is not converted back to it's hidden meaning in one particular page. 
Do ask for further clarification if still not clear.