qt: polish qt widgets before setting transient parent

See f6ce0828 for the reasoning. The same concern may apply to different widgets, such as QDialog or QWizard, that are actually windows.

modules/gui/qt/menus/menus.hpp

@@ -41,7 +41,6 @@ public:
         assert(p_intf);
         if (isWindow())
         {
-            ensurePolished();
             QVLCDialog::setWindowTransientParent(this, nullptr, p_intf);
         }
     }