Client side validations are missing at 'Create User Login' feature. Error from server side is being thrown if we do not provide the required fields.
Steps to regenerate :
1. Go to the profile page of any party.
2. Click on 'Create New' link at 'User Name(s)' section, Create User Login form will appear.
3. Do not enter any value in 'Password' field, an error from server side will come.