attempt fix for race condition

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@16064 d0543943-73ff-0310-b7d9-9358b9ac24b2

libs/sofia-sip/.update

-Mon Dec 14 15:09:49 EST 2009
+Mon Dec 28 14:17:46 EST 2009

libs/sofia-sip/libsofia-sip-ua/nua/nua_stack.c

@@ -671,7 +671,7 @@ nua_event_data_t const *nua_event_data(nua_saved_event_t const saved[1])
  */
 void nua_destroy_event(nua_saved_event_t saved[1])
 {
-  if (saved) su_msg_destroy(saved);
+  if (saved && saved[0]) su_msg_destroy(saved);
 }
 
 /** @internal Move signal. */