Merged revisions 219586 via svnmerge from

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

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  r219586 | russell | 2009-09-18 21:51:13 -0500 (Fri, 18 Sep 2009) | 6 lines
  
  Make sure the iax_pvt exists before dereferencing it.
  
  This fixes the latest crash posted on issue 15609.
  
  (issue #15609)
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git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@219587 65c4cc65-6c06-0410-ace0-fbb531ad65f3