More checks when hanging up VideoRoom subscriber (see #2087)

plugins/janus_videoroom.c

@@ -5156,22 +5156,25 @@ void janus_videoroom_hangup_media(janus_plugin_session *handle) {
 	janus_videoroom_hangup_media_internal(handle);
 }
 
-static void janus_videoroom_hangup_subscriber(janus_videoroom_subscriber * s) {
+static void janus_videoroom_hangup_subscriber(janus_videoroom_subscriber *s) {
 	/* Already hung up */
 	if (!s->feed) {
 		return;
 	}
 	/* Check if the owner needs to be cleaned up */
-	if(s->pvt_id > 0 && s->room != NULL) {
-		janus_mutex_lock(&s->room->mutex);
-		janus_videoroom_publisher *owner = g_hash_table_lookup(s->room->private_ids, GUINT_TO_POINTER(s->pvt_id));
+	janus_videoroom *room = s->room;
+	if(room != NULL)
+		janus_refcount_increase(&room->ref);
+	if(s->pvt_id > 0 && room != NULL) {
+		janus_mutex_lock(&room->mutex);
+		janus_videoroom_publisher *owner = g_hash_table_lookup(room->private_ids, GUINT_TO_POINTER(s->pvt_id));
 		if(owner != NULL) {
 			janus_mutex_lock(&owner->subscribers_mutex);
 			/* Note: we should refcount these subscription-publisher mappings as well */
 			owner->subscriptions = g_slist_remove(owner->subscriptions, s);
 			janus_mutex_unlock(&owner->subscribers_mutex);
 		}
-		janus_mutex_unlock(&s->room->mutex);
+		janus_mutex_unlock(&room->mutex);
 	}
 	/* TODO: are we sure this is okay as other handlers use feed directly without synchronization */
 	if(s->feed)
@@ -5185,6 +5188,8 @@ static void janus_videoroom_hangup_subscriber(janus_videoroom_subscriber * s) {
 		/* Remove the reference we added when "joining" the room */
 		janus_refcount_decrease(&s->ref);
 	}
+	if(room != NULL)
+		janus_refcount_decrease(&room->ref);
 }
 
 static void janus_videoroom_hangup_media_internal(janus_plugin_session *handle) {