Merged revisions 294903 via svnmerge from

Merged revisions 294903 via svnmerge from
https://origsvn.digium.com/svn/asterisk/branches/1.4

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  r294903 | jpeeler | 2010-11-12 14:49:09 -0600 (Fri, 12 Nov 2010) | 16 lines

  Fix regression causing abort in voicemail after opening a mailbox with no mesgs.

  In order to be more safe, some error handling code was changed to respect more
  error conditions including the potential memory allocation failure for deleted
  and heard message tracking introduced in 293004. However, last_message_index
  returns -1 for zero messages (perhaps as expected) and was triggering the
  stricter error checking. Because last_message_index is only called directly
  in one place, just return 0 from open_mailbox (for file based storage) when no
  messages are detected unless a real error has occurred.

  (closes issue #18240)
  Reported by: leobrown
  Patches:
        bug18240.1-6-2.diff.txt uploaded by alecdavis (license 585)
  Tested by: pabelanger
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git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.6.2@294904 65c4cc65-6c06-0410-ace0-fbb531ad65f3