Merged revisions 201380 via svnmerge from

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

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  r201380 | dbrooks | 2009-06-17 13:45:50 -0500 (Wed, 17 Jun 2009) | 9 lines
  
  Checks for NULL sip_pvt pointer in chan_sip.c->acf_channel_read()
  
  Zombie channels could be passed, and chan_sip.c wasn't checking for it.
  Could crash Asterisk. Now checking for NULL pointer.
  
  (closes issue #15330)
  Reported by: okrief
  Tested by: dbrooks
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git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@201381 65c4cc65-6c06-0410-ace0-fbb531ad65f3