gst/playback/gstplaybasebin.c: Throw error if we failed to find a suitable output...

gst/playback/gstplaybasebin.c: Throw error if we failed to find a suitable output. This should throw an error if we s...

Original commit message from CVS:
* gst/playback/gstplaybasebin.c: (gst_play_base_bin_change_state):
Throw error if we failed to find a suitable output. This should
throw an error if we successfully set up a pipeline (e.g. because
we recognized a media file) but found no decodable streams in it
(e.g. because it contains only media stream types for which we
have no decoders, or because it's not a media type).