use different constructor to more reliably set the parent for menus and actions

This may make rendering menus more stable on hi-dpi monitors.
It worked before, but sometimes it had some weird glitches.

src/plugins/domain/raction.py

@@ -76,7 +76,8 @@ class RAction():
             self._action.setText(label)
 
     def to_qaction(self, qmenu: QMenu) -> QAction:
-        action = QAction(self.label, qmenu)
+        action = QAction(qmenu)
+        action.setText(self.label)
         self._action = action
         if self.icon_from_theme:
             action.setIcon(Icon.fromTheme(self.icon_from_theme))