Tolerate mouse move generation on disposed windows.

http://crashreport.libreoffice.org/stats/crash_details/524d28fb-4fd2-4d11-83b1-1360b5ab5068

Change-Id: I19a13f751b5cf000c9938ff991d7d44bba0a4de7
Reviewed-on: https://gerrit.libreoffice.org/34756Reviewed-by: Michael Meeks <michael.meeks@collabora.com>
Tested-by: Michael Meeks <michael.meeks@collabora.com>

vcl/source/window/mouse.cxx

@@ -160,7 +160,8 @@ void Window::ImplCallMouseMove( sal_uInt16 nMouseCode, bool bModChanged )
 
 void Window::ImplGenerateMouseMove()
 {
-    if ( !mpWindowImpl->mpFrameData->mnMouseMoveId )
+    if ( mpWindowImpl && mpWindowImpl->mpFrameData &&
+         !mpWindowImpl->mpFrameData->mnMouseMoveId )
         mpWindowImpl->mpFrameData->mnMouseMoveId = Application::PostUserEvent( LINK( mpWindowImpl->mpFrameWindow, Window, ImplGenerateMouseMoveHdl ), nullptr, true );
 }