Fix sync failure if no movies/tvshows in library

Fix tvshow sync, was referencing 'tvshow' ky directly off of xbmc json request, it behaves like the movie sync code now.
Check for empty results when getting movie/tvshows from xbmc json request.
Check for empty result prior to actually performing a sync, and abort if it is empty.

This is a first crack at fixing this issue, please test and provide feedback.  Also, make sure debug setting is selected in your trakt plugin settings.