compare a NULL value with unexpected result code

[Cai Qian]

Hi,

For Perl-LDAP 0.33, I try to $ldap->compare ($entry=>dn,
attr=>'attribute', value=''), and it give me OPERATION_ERROR. However,
if I use OpenLDAP's ldapcompare with "attribute:", it give me
LDAP_COMPARE_TRUE. It seems to me Perl-LDAP sends an incorrect message
to LDPA server.

Qian