[consider merging] MainWindow should be managed (derived from gsi::ObjectBase)

src/lay/lay/layMainWindow.h

@@ -95,6 +95,7 @@ class ProgressWidget;
 class LAY_PUBLIC MainWindow
   : public QMainWindow,
     public tl::Object,
+    public gsi::ObjectBase,
     public lay::DispatcherDelegate
 {
 Q_OBJECT