reorder destruction of VCAManager and Routes

libs/ardour/session.cc

@@ -696,6 +696,11 @@ Session::destroy ()
 	DEBUG_TRACE (DEBUG::Destruction, "delete regions\n");
 	RegionFactory::delete_all_regions ();
 
+	/* Do this early so that VCAs no longer hold references to routes */
+
+	DEBUG_TRACE (DEBUG::Destruction, "delete vcas\n");
+	delete _vca_manager;
+
 	DEBUG_TRACE (DEBUG::Destruction, "delete routes\n");
 
 	/* reset these three references to special routes before we do the usual route delete thing */
@@ -748,7 +753,6 @@ Session::destroy ()
 
 	delete midi_clock;
 	delete _tempo_map;
-	delete _vca_manager;
 
 	/* clear event queue, the session is gone, nobody is interested in
 	 * those anymore, but they do leak memory if not removed