Double free crash

(closes issue #17245)
 Reported by: thedavidfactor
 Patches: 
       20100426__issue17245.diff.txt uploaded by tilghman (license 14)
 Tested by: murraytm


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@261917 65c4cc65-6c06-0410-ace0-fbb531ad65f3