fixed access violation into Storage::Unsubscribe upon deletion of UpdateDialog.

qt/mainwindow.cpp

@@ -143,6 +143,10 @@ bool MainWindow::winEvent(MSG * msg, long * result)
 MainWindow::~MainWindow()
 {
   SaveState();
+#ifndef NO_DOWNLOADER
+  if (m_updateDialog)
+    m_updateDialog->DetachFromStorage();
+#endif
 }
 
 void MainWindow::SaveState()

qt/update_dialog.cpp

@@ -88,7 +88,7 @@ namespace qt
                                             bind(&UpdateDialog::OnCountryDownloadProgress, this, _1, _2));
   }
 
-  UpdateDialog::~UpdateDialog()
+  void UpdateDialog::DetachFromStorage()
   {
     // tell download manager that we're gone...
     m_storage.Unsubscribe(m_observerSlotId);

qt/update_dialog.hpp

@@ -17,7 +17,6 @@ namespace qt
 
   public:
     explicit UpdateDialog(QWidget * parent, storage::Storage & storage);
-    ~UpdateDialog();
 
     /// @name Called from downloader to notify GUI
     //@{
@@ -28,6 +27,8 @@ namespace qt
 
     void ShowModal();
 
+    void DetachFromStorage();
+
   private slots:
     void OnItemClick(QTreeWidgetItem * item, int column);
     void OnCloseClick();