This fixes 42fcf202. A non-NULL pointer
doesn't imply that the pointer isn't an offset into a buffer object data.
Signed-off-by: Józef Kucia <jkucia@codeweavers.com>
Signed-off-by: Henri Verbeet <hverbeet@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>