Merged revisions 228418 via svnmerge from

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

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  r228418 | dvossel | 2009-11-06 11:07:13 -0600 (Fri, 06 Nov 2009) | 13 lines
  
  fixes segfault in iLBC
  
  For reasons not yet known, it appears possible for an ast_frame
  to have a datalen greater than zero while the actual data is NULL
  during Packet Loss Concealment.  Most codecs don't support PLC so
  this doesn't affect them.  This patch catches the malformed frame
  and prevents the crash from occuring.  Additional efforts to determine
  why it is possible for a frame to look like this are still being
  investigated.
  
  (issue #16979)
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git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@228420 65c4cc65-6c06-0410-ace0-fbb531ad65f3