WM_DEVICECHANGE's lParam can be either a pointer to a variant of
DEV_BROADCAST_HDR or an immediate value (usually 0) depending on
the wParam's value.

This fixes a crash when broadcasting WM_DEVICECHANGE with
wParam = DBT_DEVNODES_CHANGED, lParam = 0.
Signed-off-by: Arkadiusz Hiler <ahiler@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>