Summary:

When creating a user or group override in a Quiz where the Quiz already has a password set in 'Extra restrictions on attempts', the password in the override cannot be cleared so that it is blank. This is replicable in sandbox.moodledemo.net

Steps to replicate:

1. Enter a test course with at least 1 enrolled student user
2. Add activity or resource>Quiz
   1. Set a title and description
   2. Under 'Extra restrictions on attempts' set Password to 'password'
   3. Save and display
3. Go to More>Overrides
4. Add a new user override (the same occurs with group, but for simplicity user is easier)
5. Select a user from the dropdown
6. Edit the password and delete it completely
7. Change another setting like the start or end date to ensure a change is registered and the form can be saved (this is due to MDL-82026 and other similar tracker items)
8. Save the override
9. Edit the override again and view the password

Observed behaviour:

The password, even though it has been cleared and saved, reverts to 'password', which was set in the Quiz activity settings

Expected behaviour:

The password for the override is blank such that no password is required for the user/override