So that the hook is properly removed on failure in wined3d_swapchain_create().
This is a somewhat theoretical though, since in practice
WINED3D_SWAPCHAIN_HOOK and WINED3D_SWAPCHAIN_IMPLICIT are never used together.
Signed-off-by: Henri Verbeet <hverbeet@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>