output/jack: check for connection failure before starting playback

NEWS

@@ -4,6 +4,7 @@ ver 0.16.8 (2012/??/??)
   - vorbis (and others): fix seeking at startup
   - ffmpeg: read the "year" tag
 * output:
+  - jack: check for connection failure before starting playback
   - jack: workaround for libjack1 crash bug
   - osx: fix stuttering due to buffering bug
 * fix endless loop in text file reader

src/output/jack_output_plugin.c

@@ -576,6 +576,9 @@ mpd_jack_open(void *data, struct audio_format *audio_format, GError **error_r)
 
 	jd->pause = false;
 
+	if (jd->client != NULL && jd->shutdown)
+		mpd_jack_disconnect(jd);
+
 	if (jd->client == NULL && !mpd_jack_connect(jd, error_r))
 		return false;