Apparently, in certain cases, a callno is already destroyed when iax2_destroy is called.

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@131480 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_iax2.c

@@ -1305,7 +1305,7 @@ retry:
 			goto retry;
 		}
 	}
-	if (!owner) {
+	if (!owner && iaxs[callno]) {
 		AST_SCHED_DEL(sched, iaxs[callno]->lagid);
 		AST_SCHED_DEL(sched, iaxs[callno]->pingid);
 		iaxs[callno] = NULL;