Timed-out lesson attempts cannot be deleted successfully

1. Create a lesson and enable the timer
2. As a student, start the lesson and then just leave it without answering any questions
3. When the timer runs out the gradebook will initially show no record of the attempt, and the lesson report will similarly not list the attempt
4. As the student again, return to the lesson
5. You will see a message that your attempt timed out and a notice of your grade
6. The grade will appear in the gradebook, but will not be listed on the lesson reports screen
7. Unlike other attempts, therefore, the unfinished attempt cannot be deleted

If you partially complete a lesson, then attempt will show up under that lesson's reports, and it can apparently be deleted, but when the student tries again to complete the lesson, they will see this error:

>Error: could not find lesson_timer records