Kong Manager User Delete issue

I had registered one user by inviting him through Teams → Invite Admin option. After registration, everything worked fine like link for registration, password set by user and then login with his password.
I deleted that user and sent invitation again but user is not able to re-register himself by registration link.

What I noticed is while deleting that user through option Teams → click on edit option of that user → Delete Admin, I saw below error logs in my container logs. On the manager screen there was no error.

 [error] 2066#0: *18642 [lua] events.lua:194: do_handlerlist(): worker-events: event callback failed; source=dao:crud, event=delete, pid=nil error='/usr/local/share/lua/5.1/kong/db/dao/rbac_role_entities.lua:17: attempt to concatenate local 'id' (a nil value)
stack traceback:
        /usr/local/share/lua/5.1/kong/db/dao/rbac_role_entities.lua:17: in function 'cache_key'
        /usr/local/share/lua/5.1/kong/runloop/handler.lua:416: in function </usr/local/share/lua/5.1/kong/runloop/handler.lua:402>
        [C]: in function 'xpcall'
        /usr/local/share/lua/5.1/resty/worker/events.lua:185: in function 'do_handlerlist'
        /usr/local/share/lua/5.1/resty/worker/events.lua:217: in function 'do_event'
        /usr/local/share/lua/5.1/resty/worker/events.lua:291: in function 'post_local'
        /usr/local/share/lua/5.1/kong/db/dao/init.lua:1465: in function 'post_crud_event'