The bug is only cosmetic. It is pretty safe to edit LDAP. If it goes wrong you can do a configuration restore. If you don't want to do that, create an rsyslog configlet to drop the messages. To do a proper fix now is out of the question as it needs an expert who can program all group removal from LDAP before deleting the user. Realistically, this is not going to happen in 7.x.

Has this been been resolved or trick. (not editing LDAP)
I'm having the same issue and the bug is know since 2014

IIRC it is a long-standing bug. You can either ignore it or take your life into your hands and edit LDAP. Back it up first with a "slapcat -n3 > file". Get hold of a copy of phpldapadmin and then you need to edit your LDAP database. I don't know if you can view it but the bug is here. You need to remove the user from all groups he has been left in. I don't think you should leave any group empty and there may be a default value you need in an empty group.