GetDesktopWindow incorrectly assumes, that the process window station is
still the same one, which was used earlier when changing the desktop.
By moving the visibility check to wineserver we can also avoid
wineserver roundtrip for invisible desktops.
Signed-off-by: Sebastian Lackner <sebastian@fds-team.de>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>