Fix a crash that happened due to accessing free'd memory

(closes issue #12396)
Reported by: tcalosi
Patches:
      12396.patch uploaded by putnopvut (license 60)
	  Tested by: tcalosi


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@113980 65c4cc65-6c06-0410-ace0-fbb531ad65f3