Issue Description

dsconf fails with ERROR: Error: values has to be a tuple, was None when adding a new objectClass

Package Version and Platform:

1.4.4.3+

Steps to Reproduce

[root@server-f33 ds]# dsconf -v server-f33 schema objectclasses add testOC 
DEBUG: The 389 Directory Server Configuration Tool
DEBUG: Inspired by works of: ITS, The University of Adelaide
DEBUG: dsrc path: /root/.dsrc
DEBUG: dsrc container path: /data/config/container.inf
DEBUG: dsrc instances: []
DEBUG: dsrc no such section: slapd-server-f33
DEBUG: Called with: Namespace(instance='server-f33', verbose=True, binddn=None, bindpw=None, prompt=False, pwdfile=None, basedn=None, starttls=False, json=False, name='testOC', oid=None, desc=None, x_origin=None, must=None, may=None, kind=None, sup=None, func=<function add_objectclass at 0x7f5917562dc0>)
DEBUG: Instance details: {'uri': 'server-f33', 'basedn': None, 'binddn': None, 'bindpw': None, 'saslmech': None, 'tls_cacertdir': None, 'tls_cert': None, 'tls_key': None, 'tls_reqcert': None, 'starttls': False, 'prompt': False, 'pwdfile': None, 'args': {'ldapurl': 'server-f33', 'root-dn': None}}
DEBUG: Allocate <class 'lib389.DirSrv'> with ldapi://%2fvar%2frun%2fslapd-server-f33.socket
DEBUG: Allocate <class 'lib389.DirSrv'> with %2fvar%2frun%2fslapd-server-f33.socket
DEBUG: Allocate <class 'lib389.DirSrv'> with server-f33.example.com:389
DEBUG: Allocate <class 'lib389.DirSrv'> with server-f33.example.com:389
DEBUG: Allocate <class 'lib389.DirSrv'> with ldapi://%2fvar%2frun%2fslapd-server-f33.socket
DEBUG: Allocate <class 'lib389.DirSrv'> with %2fvar%2frun%2fslapd-server-f33.socket
DEBUG: Allocate <class 'lib389.DirSrv'> with server-f33.example.com:389
DEBUG: Allocate <class 'lib389.DirSrv'> with server-f33.example.com:389
DEBUG: open(): Connecting to uri ldapi://%2fvar%2frun%2fslapd-server-f33.socket
DEBUG: Using dirsrv ca certificate /etc/dirsrv/slapd-server-f33
DEBUG: Using external ca certificate /etc/dirsrv/slapd-server-f33
DEBUG: Using external ca certificate /etc/dirsrv/slapd-server-f33
DEBUG: Using /etc/openldap/ldap.conf certificate policy
DEBUG: ldap.OPT_X_TLS_REQUIRE_CERT = 2
DEBUG: open(): Using root autobind ...
DEBUG: open(): bound as None
DEBUG: Retrieving entry with [('',)]
DEBUG: Retrieved entry [dn: 
vendorVersion: 389-Directory/2.0.3.20210309gitaefc1acbf B2021.068.1215

]
DEBUG: cn=schema get_attr_vals('objectClasses')
DEBUG: values has to be a tuple, was None
Traceback (most recent call last):
  File "/usr/sbin/dsconf", line 134, in <module>
    result = args.func(inst, None, log, args)
  File "/usr/lib/python3.9/site-packages/lib389/cli_conf/schema.py", line 144, in add_objectclass
    schema.add_objectclass(parameters)
  File "/usr/lib/python3.9/site-packages/lib389/schema.py", line 330, in add_objectclass
    return self._add_schema_object(parameters, ObjectClass)
  File "/usr/lib/python3.9/site-packages/lib389/schema.py", line 215, in _add_schema_object
    return self.add(attr_name, str(schema_object))
  File "/usr/lib64/python3.9/site-packages/ldap/schema/models.py", line 179, in __str__
    result.append(self.key_list('X-ORIGIN',self.x_origin,quoted=1))
  File "/usr/lib64/python3.9/site-packages/ldap/schema/models.py", line 79, in key_list
    assert type(values)==tuple,TypeError("values has to be a tuple, was %r" % values)
AssertionError: values has to be a tuple, was None
ERROR: Error: values has to be a tuple, was None