missing part of RCU update for tempo marker drag

gtk2_ardour/editor_drag.cc

@@ -3687,8 +3687,16 @@ TempoMarkerDrag::finished (GdkEvent* event, bool movement_occurred)
 		return;
 	}
 
+	/* push the current state of our writable map copy */
+
 	TempoMap::SharedPtr map (TempoMap::use());
 
+	TempoMap::update (map);
+
+	/* fetch it back into our local copy */
+
+	map = TempoMap::use();
+
 	XMLNode &after = map->get_state();
 
 	_editor->session()->add_command (new MementoCommand<Temporal::TempoMap> (new Temporal::TempoMap::MementoBinder(), _before_state, &after));