Prevent re-replacing state in setGeometry

Do not allow replacing a state again if it is already being replaced.

Cleaned up from the patch provided in QTBUG-121126.

Fixes: QTBUG-121126
Pick-to: 6.6 6.7
Change-Id: Icca932b0e5cccd2f39ac18f29d8f7707887d147f
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

src/widgets/widgets/qmainwindowlayout.cpp

@@ -2230,7 +2230,9 @@ void QMainWindowLayout::applyRestoredState()
 
 void QMainWindowLayout::setGeometry(const QRect &_r)
 {
-    if (savedState.isValid())
+    // Check if the state is valid, and avoid replacing it again if it is currently used
+    // in applyState
+    if (savedState.isValid() || (restoredState && isInApplyState))
         return;
 
     QRect r = _r;