videodb: clean tvshows without episodes independent of their configuration as a source

Stumbled upon this while looking into an issue with clean library.

IMO this additional WHERE condition doesn't make sense on the tvshow table (it's perfectly fine on the path table though). What this means is that when you have a video source containing a single tvshow and you delete either all episodes of the tvshow or even the entire tvshow (i.e. the entire source) the tvshow will still be listed in your library but it will be empty.