Merged revisions 320504 via svnmerge from

Merged revisions 320504 via svnmerge from
https://origsvn.digium.com/svn/asterisk/branches/1.8

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  r320504 | jrose | 2011-05-23 09:33:20 -0500 (Mon, 23 May 2011) | 10 lines

  Fixes segfault occuring in chan_sip.c at __set_address_from_contact

  Checks to see if domain contains anything before sending it off to ast_sockaddr_resolve
  which is where the segfault was occuring due to null str.

  (closes issue #18857)
  Reported by: sybasesql

  Review: https://reviewboard.asterisk.org/r/1225/
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git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@320505 65c4cc65-6c06-0410-ace0-fbb531ad65f3