Dont coredump on register of non-configured devices

(closes issue #13224)
Reported by: mvanbaak
Patches:
      noncon.diff uploaded by wedhorn (license 30) with whitespace fixes by me
Tested by: wedhorn, mvanbaak


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@135371 65c4cc65-6c06-0410-ace0-fbb531ad65f3