Steps to reproduce:

1. Open Users -> Authentication -> LDAP settings
2. Enable LDAP authentication with JIT provisioning
3. Configure LDAP server with at least 2 media type mappings
4. Click Update
5. Re-open the LDAP server's configuration
6. Remove the first media type mapping
7. Click Update

Result:

Console error is displayed: 

TypeError: ldap.provision_media.entries is not a function or its return value is not iterable

See video:

Expected:
No errors should be displayed. Should be possible to remove the media type mapping and update the configuration.