renderer: Accept missing mime type in AVTransport.is_playlist()
renderer: Accept missing mime type in AVTransport.is_playlist()

"assertion 'mime != NULL' failed" is not useful here.

https://bugzilla.gnome.org/show_bug.cgi?id=711661

GNOME/rygel,Pelagicore/Media-Manager-Rygel-patched,Pelagicore/Media-Manager-Rygel-patched,Pelagicore/Media-Manager-Rygel-patched,Tarnyko/rygel,GNOME/rygel,GNOME/rygel,Tarnyko/rygel