Merged revisions 159269 via svnmerge from

https://origsvn.digium.com/svn/asterisk/branches/1.4

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  r159269 | tilghman | 2008-11-25 15:56:48 -0600 (Tue, 25 Nov 2008) | 7 lines
  
  Don't try to send a response on a NULL pvt.
  (closes issue #13919)
   Reported by: barthpbx
   Patches: 
         chan_iax2.c.patch uploaded by eliel (license 64)
   Tested by: barthpbx
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git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@159276 65c4cc65-6c06-0410-ace0-fbb531ad65f3