output/jack: workaround for libjack1 crash bug

NEWS

@@ -4,6 +4,7 @@ ver 0.16.8 (2012/??/??)
   - vorbis (and others): fix seeking at startup
   - ffmpeg: read the "year" tag
 * output:
+  - jack: workaround for libjack1 crash bug
   - osx: fix stuttering due to buffering bug
 * fix endless loop in text file reader
 * update: skip symlinks in path that is to be updated

src/output/jack_output_plugin.c

@@ -143,6 +143,13 @@ mpd_jack_process(jack_nframes_t nframes, void *arg)
 
 	for (unsigned i = 0; i < jd->audio_format.channels; ++i) {
 		out = jack_port_get_buffer(jd->ports[i], nframes);
+		if (out == NULL)
+			/* workaround for libjack1 bug: if the server
+			   connection fails, the process callback is
+			   invoked anyway, but unable to get a
+			   buffer */
+			continue;
+
 		jack_ringbuffer_read(jd->ringbuffer[i],
 				     (char *)out, available * jack_sample_size);
 
@@ -156,6 +163,12 @@ mpd_jack_process(jack_nframes_t nframes, void *arg)
 	for (unsigned i = jd->audio_format.channels;
 	     i < jd->num_source_ports; ++i) {
 		out = jack_port_get_buffer(jd->ports[i], nframes);
+		if (out == NULL)
+			/* workaround for libjack1 bug: if the server
+			   connection fails, the process callback is
+			   invoked anyway, but unable to get a
+			   buffer */
+			continue;
 
 		for (jack_nframes_t f = 0; f < nframes; ++f)
 			out[f] = 0.0;