Unable to change password with TLJH JupyterHub 4.0.2

Hello, when trying to change a password, I get a 500 error.
`journalctl -u jupyterhub`
```
Oct 11 15:34:24 servername python3[123]: [E 2023-10-11 15:34:24.227 JupyterHub web:1871] Uncaught exception POST /hub/change-password (172.16._._)
Oct 11 15:34:24 servername python3[123]: HTTPServerRequest(protocol='https', host='jupyter.example.com', method='POST', uri='/hub/change-password', version='HTTP/1.1', remote_ip='172.16._._')
Oct 11 15:34:24 servername python3[123]: Traceback (most recent call last):
Oct 11 15:34:24 servername python3[123]: File "/opt/tljh/hub/lib/python3.10/site-packages/tornado/web.py", line 1786, in _execute
Oct 11 15:34:24 servername python3[123]: result = await result
Oct 11 15:34:24 servername python3[123]: File "/opt/tljh/hub/lib/python3.10/site-packages/nativeauthenticator/handlers.py", line 348, in post
Oct 11 15:34:24 servername python3[123]: ).is_valid_password(old_password)
Oct 11 15:34:24 servername python3[123]: AttributeError: 'NoneType' object has no attribute 'is_valid_password'
```
It seems self.authenticator.get_user(user.name) in handlers.py is returning None. This has happened after I recently tried to enable NativeAuthenticator via `sudo tljh-config set auth.type nativeauthenticator.NativeAuthenticator`. The user I was trying to change the password for was an admin user that I have originally set up prior to telling it to use NativeAuthenticator.

Any assistance in resolving this issue would be greatly appreciated.