#4312 Move handleMdiWindowClosed call from widget destructors to MdiSubWindow closeEvent

* This way the mdi window still exists at the time of removal and we can handle the removal orderly

ApplicationCode/UserInterface/RiuMainWindowBase.h

@@ -31,6 +31,7 @@ namespace caf
 }
 
 
+class QMdiArea;
 class QMdiSubWindow;
 
 
@@ -72,6 +73,9 @@ public:
     void                setBlockSlotSubWindowActivated(bool block);
     bool                blockSlotSubWindowActivated() const;
 
+protected:
+    void                removeViewerFromMdiArea(QMdiArea* mdiArea, QWidget* viewer);
+
 protected slots:
     void                slotDockWidgetToggleViewActionTriggered();
     void			    addViewerToMdiArea(QMdiArea* mdiArea, QWidget* viewer, const QPoint& subWindowPos, const QSize& subWindowSize);