fix: if a CANCEL to non-existing call received, reply 481 error

git-svn-id: http://svn.berlios.de/svnroot/repos/sems/trunk@1473 8eb893ce-cfd4-0310-b710-fb5ebe64c474

core/AmSipDispatcher.cpp

@@ -94,8 +94,14 @@ void AmSipDispatcher::handleSipMsg(AmSipRequest &req)
       // Basic OPTIONS support
       AmSipDialog::reply_error(req,200,"OK");
       return;
-  }
-  else {
+
+  } else if(req.method == "CANCEL"){      
+    // CANCEL to a (here) non-existing dialog
+    AmSipDialog::reply_error(req,481,
+			     "Call leg/Transaction does not exist");
+    return;
+
+  } else {
 
       AmSessionFactory* sess_fact = AmPlugIn::instance()->findSessionFactory(req);
       if(!sess_fact){