tdf#115315 Cursor not in focus with new document

Partial revert of 7aae8772
("Clear VclPtr instance reference on removed UserEvents.")
Disposing of child controls should not affect focus events
of the parent frame.

Change-Id: I583311050560a2851cfcc372741b675b52375d06
Reviewed-on: https://gerrit.libreoffice.org/49855Reviewed-by: Maxim Monastirsky <momonasmon@gmail.com>
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Michael Meeks <michael.meeks@collabora.com>

vcl/source/window/window.cxx

@@ -489,7 +489,7 @@ void Window::dispose()
     if ( pSVData->maWinData.mpLastDeacWin == this )
         pSVData->maWinData.mpLastDeacWin = nullptr;
 
-    if ( mpWindowImpl->mpFrameData )
+    if ( mpWindowImpl->mbFrame && mpWindowImpl->mpFrameData )
     {
         if ( mpWindowImpl->mpFrameData->mnFocusId )
             Application::RemoveUserEvent( mpWindowImpl->mpFrameData->mnFocusId );