QMainWindow:.tabifiedDockWidgets() was refactored in Qt 6.6.3, because
it returned wrong values. It now loops from 0 to
QMainWindowTabBar::count() and uses QMainWindowTabBar::dockAt(), to
get the dock widget pointer for an index.
When a dock widget is removed from a floating tab, event processing is
necessary for the item_list and QMainWindowTabBar::count() to get in
sync. This case was overlooked in the refactoring. It can lead to
dockAt() being called with an out-of-bounds index, which it asserted.
The assertion triggered, when QMainWindow::removeDockWidget() and
QMainWindow::tabifiedDockWidgets() were called right after each other,
without processing events inbetween.
QMainWindowTabBar::dockWidgets() doesn't add nullptr to the list, it
returns.
Therefore, return nullptr, when dockAt() is called out-of-bounds.
Add test functionality in
tst_QDockWidget::updateTabBarOnVisibilityChanged().
Fixes: QTBUG-124262
Pick-to: 6.7 6.5
Change-Id: If66084b9f00b4e39f7a620da68df67c735029cf1
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
f97e60a4f0