* nua: try to cope if a re-INVITE nor its ACK contain SDP
  
  Some SIP user-agents use INVITE without SDP offer to refresh session.
  By default, NUA sends an offer in 200 OK to such an INVITE and expects
  an answer back in ACK. Now nua tries to recover from such a Offer/Answer
  protocol error.
  
  Also, if NUTAG_REFRESH_WITHOUT_SDP(1) tag is used, and if the re-INVITE was
  received without SDP, no SDP offer is sent in 200 OK.
  
  Thanks for Anthony Minessale for reporting the problem.



git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@10829 d0543943-73ff-0310-b7d9-9358b9ac24b2