Avoid dialog and other widgets with non-adjusted window flags.

Reviewed-by: Samuel Rødal

src/widgets/kernel/qwidget_qpa.cpp

@@ -233,6 +233,7 @@ void QWidgetPrivate::setParent_sys(QWidget *newparent, Qt::WindowFlags f)
         q->destroy();
     }
 
+    adjustFlags(f, q);
     data.window_flags = f;
     q->setAttribute(Qt::WA_WState_Created, false);
     q->setAttribute(Qt::WA_WState_Visible, false);