sw lok comments: avoid crash an exit after clicking the scrollbar

Without this, vcl::Window::ImplTrackTimerHdl() will be called on a
deleted vcl::Window.

Can be reproduced with a comment having a scrollbar in a LOK client,
then clicking on the down button of the scrollbar a number of times ->
crash on exit.

Change-Id: I5d67f96e8baa199f65ec5cf39cb5d39c8162ff33
(cherry picked from commit 7c654ee9)

sw/source/uibase/docvw/SidebarScrollBar.cxx

@@ -60,6 +60,11 @@ void SidebarScrollBar::LogicInvalidate(const Rectangle* pRectangle)
     rWrtShell.libreOfficeKitCallback(LOK_CALLBACK_INVALIDATE_TILES, sRectangle.getStr());
 }
 
+void SidebarScrollBar::MouseButtonUp(const MouseEvent& /*rMouseEvent*/)
+{
+    EndTracking();
+}
+
 void SidebarScrollBar::MouseMove(const MouseEvent& rMouseEvent)
 {
     TrackingEvent aEvent(rMouseEvent);

sw/source/uibase/docvw/SidebarScrollBar.hxx

@@ -31,6 +31,7 @@ protected:
     /// @see OutputDevice::LogicInvalidate().
     void LogicInvalidate(const Rectangle* pRectangle) override;
     void MouseMove(const MouseEvent& rMouseEvent) override;
+    void MouseButtonUp(const MouseEvent& rMouseEvent) override;
 public:
     SidebarScrollBar(SwSidebarWin& rSidebarWin, WinBits nStyle, SwView& rView);
     virtual ~SidebarScrollBar();