ensure that app_queue won't crash if no members are defined via Realtime (issue #5300)

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@6693 65c4cc65-6c06-0410-ace0-fbb531ad65f3

apps/app_queue.c

@@ -875,6 +875,11 @@ static int join_queue(char *queuename, struct queue_ent *qe, enum queue_result *
 	if(queue_vars)
 		member_config = ast_load_realtime_multientry("queue_members", "interface LIKE", "%", "queue_name", queuename, NULL);
 	
+	if (!member_config) {
+		ast_log(LOG_ERROR, "no queue_members defined in your config (extconfig.conf).\n");
+		return res;
+	}
+
 	ast_mutex_lock(&qlock);
 	q = reload_queue_rt(queuename, queue_vars, member_config);
 	/* Note: If found, reload_queue_rt() returns with q->lock locked. */