Don't crash if the iax2 pvt structure has been destroyed before we get to this point

(closes issue #11672, reported by snuffy, patched by me)


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@96394 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_iax2.c

@@ -8250,11 +8250,11 @@ retryowner2:
 	iax_frame_wrap(fr, &f);
 
 	/* If this is our most recent packet, use it as our basis for timestamping */
-	if (iaxs[fr->callno]->last < fr->ts) {
+	if (iaxs[fr->callno] && iaxs[fr->callno]->last < fr->ts) {
 		/*iaxs[fr->callno]->last = fr->ts; (do it afterwards cos schedule/forward_delivery needs the last ts too)*/
 		fr->outoforder = 0;
 	} else {
-		if (option_debug && iaxdebug)
+		if (option_debug && iaxdebug && iaxs[fr->callno])
 			ast_log(LOG_DEBUG, "Received out of order packet... (type=%d, subclass %d, ts = %d, last = %d)\n", f.frametype, f.subclass, fr->ts, iaxs[fr->callno]->last);
 		fr->outoforder = -1;
 	}