#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/RiuQwtPlot.cpp

@@ -92,11 +92,7 @@ RiuQwtPlot::~RiuQwtPlot()
     if (ownerPlotDefinition())
     {
         ownerPlotDefinition()->detachAllCurves();
-    }
-    if (ownerViewWindow())
-    {
-        ownerViewWindow()->handleMdiWindowClosed();
-    }
+    }  
 }
 
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