As discovered by OlgaK in MDLQA-11054:

1. Use Clean theme.
2. Add a new workshop and select Rubric as the grading strategy.
3. Edit the assessment form and enter some text for the Criterion 1 description only.
4. Click 'Save and preview'

Expected result:

You are prevented from saving the form because no level definitions are filled in.

Actual result:

The form is saved and is displayed with a notice:

Notice: Undefined variable: type in /var/www/vhosts/qa.moodle.net/html/lib/pear/HTML/QuickForm/group.php on line 286