(ITS#8266) empty ldapmodify refused with slapo-unique

Full_Name: Geert Hendrickx Version: 2.4.42 OS: URL: ftp://ftp.openldap.org/incoming/ Submission from: (NULL) (212.123.14.2)

When slapo-unique constraints are in effect, it seems empty updates are no longer allowed:

$ ldapmodify -x -h localhost -D cn=Manager,dc=my-domain,dc=com -w secret dn: cn=test1,dc=my-domain,dc=com changetype: modifyA%A modifying entry "cn=test1,dc=my-domain,dc=com" ldap_modify: Invalid syntax (21) additional info: unique_modify() got null op.orm_modlist

Why is this considered invalid syntax? Without slapo-unique constraint, empty updates like these are accepted.