nua_session.c: fixed call state reporting from failed INVITE

If INVITE was returned a failure response, and session was being terminated
(like BYE was sent while INVITE transaction was on-going), Sofia reported
session as already terminated.

darcs-hash:20080407172055-65a35-d7d93446327fa03ace8ff83f4ca901734321afca.gz

libsofia-sip-ua/nua/nua_session.c

@@ -3932,6 +3932,8 @@ static void signal_call_state_change(nua_handle_t *nh,
 	ss->ss_state = next_state;
       else if (ss->ss_state == nua_callstate_ready)
 	next_state = ss->ss_state;
+      else if (ss->ss_state == nua_callstate_terminating)
+	return;
       else 
 	ss->ss_state = next_state = nua_callstate_terminated;
     }