IPADDRESS_GetPartIndex() is also used for handling WM_KILLFOCUS
and WM_SETFOCUS messages. In this case, it's actually expected that the
window receiving or losing focus may not be a IP Address part window.
Signed-off-by: Zhiyi Zhang <zzhang@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>