Don't assume the callid of a dialog will be set, as in some circumstances it may not. (issue #9534 reported by tecnoxarxa)

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@61641 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -4354,6 +4354,8 @@ static struct sip_pvt *find_call(struct sip_request *req, struct sockaddr_in *si
 	for (p = iflist; p; p = p->next) {
 		/* In pedantic, we do not want packets with bad syntax to be connected to a PVT */
 		int found = FALSE;
+		if (ast_strlen_zero(p->callid))
+			continue;
 		if (req->method == SIP_REGISTER)
 			found = (!strcmp(p->callid, callid));
 		else