RegGetValueW doesn't return ERROR_MORE_DATA when the buffer parameter
is NULL, unlike other Reg functions. This also passes the correct
parameter(reg_driver) on the second call to RegGetValueW.
Signed-off-by: Alistair Leslie-Hughes <leslie_alistair@hotmail.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>