FreeSWITCH-event-for-gateway-ping

make sure sip->sip_request->rq_url->url_user exists before you strncmp on it.

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@11589 d0543943-73ff-0310-b7d9-9358b9ac24b2