While re-testing backup/restore for MDL-71696, I've faced the following issue: "Notice: Undefined index: category in moodle/question/type/edit_question_form.php on line 871". However, it's unrelated to the patch (I've been able to reproduce it in Moodle 3.11 too).

Steps to reproduce it

1. Restore the attached backup (created with Moodle 3.11): backup-moodle2-course-4-activity_examples-20220202-1815-nu.mbz
2. Access to the quiz and edit the first question, "Moodle activities" (although I think it's happening with any of the questions).
3. Modify the "Question text" and save changes.

Expected behaviour

Question is saved and changes are displayed when previewing the question.

Current behaviour

The previous error will be displayed and changes won't be saved.