Do not create a publisher stream entry for rejected SDP offer m-line.

Entering a stream into the publisher instance will cause an
m-line in any subsequent subscription request for that publisher to
attempt to create an m-line for a codec named 'none',
which will cause the operation to fail.

src/plugins/janus_videoroom.c

@@ -11911,7 +11911,9 @@ static void *janus_videoroom_handler(void *data) {
 								JANUS_SDP_OA_ACCEPT_EXTMAP, videoroom->audiolevel_ext ? JANUS_RTP_EXTMAP_AUDIO_LEVEL : NULL,
 							JANUS_SDP_OA_DONE);
 						janus_sdp_mline *m_answer = janus_sdp_mline_find_by_index(answer, m->index);
-						if(m_answer != NULL) {
+						if(m_answer == NULL || m_answer->port == 0) {
+							new_ps = FALSE;
+						} else {
 							/* TODO Remove, this is just here for backwards compatibility */
 							if(audiocodec == NULL)
 								audiocodec = janus_audiocodec_name(ps->acodec);
@@ -11932,7 +11934,9 @@ static void *janus_videoroom_handler(void *data) {
 								JANUS_SDP_OA_ACCEPT_EXTMAP, videoroom->transport_wide_cc_ext ? JANUS_RTP_EXTMAP_TRANSPORT_WIDE_CC : NULL,
 							JANUS_SDP_OA_DONE);
 						janus_sdp_mline *m_answer = janus_sdp_mline_find_by_index(answer, m->index);
-						if(m_answer != NULL) {
+						if(m_answer == NULL || m_answer->port == 0) {
+							new_ps = FALSE;
+						} else {
 							/* TODO Remove, this is just here for backwards compatibility */
 							if(videocodec == NULL)
 								videocodec = janus_videocodec_name(ps->vcodec);