windows: Allow GUID with and without trailing zeroes

Improve the GUID length check to accommodate the cases where the GUID
string fetched from registry does not have a trailing zero, or if a
multi-string entry, one or two trailing zeroes.

Closes #927

Signed-off-by: Craig Hutchinson <54269136+CraigHutchinson@users.noreply.github.com>
[Tormod: Use correct types and simplify comparisons]
Signed-off-by: Tormod Volden <debian.tormod@gmail.com>
Signed-off-by: Nathan Hjelm <hjelmn@google.com>
2 files changed