When a window is closed, then it will cause the child windows to be
closed as well as a result. Therefore in order to ensure that they are
shown again as a result, we need to remove the WA_WState_ExplicitShowHide
attribute if the widget was not already hidden before. This enables us to
test for this attribute when calling showChildren(), so that if the
window has a windowHandle then we can make sure that this widget is shown
again.
Fixes: QTBUG-73021
Change-Id: I1186242b889899dfcd38d782a67567348e2055ee
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
ccd3bf0871