Bug#1001082: qtbase-opensource-src: segfault when closing one windows in a multi window QT application

[theofficialgman]

any updates on this? as referenced before, it should be fixable by picking
these two commits:
https://codereview.qt-project.org/c/qt/qtbase/+/264529
https://codereview.qt-project.org/c/qt/qtbase/+/237817
which were used to resolve this bug:
https://bugreports.qt.io/browse/QTBUG-68393