QMainWindowLayout::animationFinished(): don't show deleted tab bars

QMainWindowLayout::animationFinished(): looped over a copy of the
usedTabBars member and showed all tab bars in the container.
Showing a tab bar, can cause another in the container to become unused.
Unused tab bars were kept in a separate container and re-used, before
a3f0ce4c0d0627ef979052b34b21e6fd2bdc3acf changed this logic and deleted
unused tab bars.

This caused a regression: show() was called on a deleted tab bar,
causing a crash.

Only show tab bars from the copied container, if usedTabBars still
contains them.

Fixes: QTBUG-138201
Pick-to: 6.10 6.9
Change-Id: I33de57ab3276d1f786d27f63aebfe8ba8ddc2832
Reviewed-by: Samuel Gaist <[email protected]>
Reviewed-by: Marc Mutz <[email protected]>

1 files changed, 4 insertions, 2 deletions

diff --git a/src/widgets/widgets/qmainwindowlayout.cpp b/src/widgets/widgets/qmainwindowlayout.cpp
index 87c33932a8d..a1a4cfc2ce0 100644
--- a/src/widgets/widgets/qmainwindowlayout.cpp
+++ b/src/widgets/widgets/qmainwindowlayout.cpp
@@ -2673,8 +2673,10 @@ void QMainWindowLayout::animationFinished(QWidget *widget)
         parentWidget()->update(layoutState.dockAreaLayout.separatorRegion());
 #if QT_CONFIG(tabbar)
         const auto usedTabBarsCopy = usedTabBars; // list potentially modified by animations
-        for (QTabBar *tab_bar : usedTabBarsCopy)
-            tab_bar->show();
+        for (QTabBar *tab_bar : usedTabBarsCopy) {
+            if (usedTabBars.contains(tab_bar)) // Showing a tab bar can cause another to be deleted.
+               tab_bar->show();
+        }
 #endif // QT_CONFIG(tabbar)
 #endif // QT_CONFIG(dockwidget)
     }