libcli/security: conditional aces: don't allow U+0000 in unicode

libcli/security: conditional aces: don't allow U+0000 in unicode

Allowing this broke a round-trip decode-encode fuzz test. Credit to OSS-Fuzz.

REF: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=62742

(Comments are from an earlier commit by Douglas Bagnall <douglas.bagnall@catalyst.net.nz>)

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Reviewed-by: Joseph Sutton <josephsutton@catalyst.net.nz>
Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Mon Nov 13 02:30:23 UTC 2023 on atb-devel-224