app_queue segfaults if realtime field uniqueid is NULL

(closes issue #16385)
Reported by: haakon
Patches:
      app_queue.c.patch uploaded by haakon (license 880)
      app_queue.c.patch_v2 uploaded by dvossel (license 671)
Tested by: haakon



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@237327 65c4cc65-6c06-0410-ace0-fbb531ad65f3