playbin: shows no-audio when it's unsupported audio and does not show tags
Submitted by Bastien Nocera
(totem:10216): GStreamer-WARNING **: pad asfdemux0:audio_00 returned caps that are not a real subset of its template caps
** Message: don't know how to handle EMPTY
EMPTY in this case actually contains "Voxware Metasound" audio, which can be played with the right win32 DLLs installed.