Merged revisions 105005 via svnmerge from

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

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r105005 | qwell | 2008-02-28 13:20:10 -0600 (Thu, 28 Feb 2008) | 9 lines

Make pbx_exec pass an empty string into applications, if we get NULL.
This protects against possible segfaults in applications that may try
 to use data before checking length (ast_strdupa'ing it, for example)

(closes issue #12100)
Reported by: foxfire
Patches:
      12100-nullappargs.diff uploaded by qwell (license 4)

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