Add check for the GPO link to have at least two attributes separated by semicolumn...

Add check for the GPO link to have at least two attributes separated by semicolumn. Allows to handle empty links.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15877
RN: Fix handling of empty GPO link

Singed-off-by: Alex Sharov (kororland@gmail.com)
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andreas Schneider <asn@samba.org>
Autobuild-User(master): Andreas Schneider <asn@cryptomilk.org>
Autobuild-Date(master): Thu Jul 10 18:55:33 UTC 2025 on atb-devel-224

(cherry picked from commit 44ee31c0258b0afb3d3f2ce17942cc86e308a690)

Autobuild-User(v4-21-test): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(v4-21-test): Thu Jul 31 14:51:55 UTC 2025 on atb-devel-224