Address the condition where X-ClientCode could be NULL or an empty string - from a -dev posting.

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@8058 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -8735,7 +8735,7 @@ static void handle_request_info(struct sip_pvt *p, struct sip_request *req)
 			ast_queue_control(p->owner, AST_CONTROL_VIDUPDATE);
 		transmit_response(p, "200 OK", req);
 		return;
-	} else if ((c = get_header(req, "X-ClientCode"))) {
+	} else if (!ast_strlen_zero(c = get_header(req, "X-ClientCode"))) {
 		/* Client code (from SNOM phone) */
 		if (ast_test_flag(p, SIP_USECLIENTCODE)) {
 			if (p->owner && p->owner->cdr)