Steps to reproduce

1. As admin create a course, set to Single activity course format, with a Quiz activity.
2. Ensure the course is visible to students.
3. Go into the course.
4. Set up the quiz, including setting it to Hidden under common module settings.
5. Log in as student.
6. Try to go into the course.

Actual result:

• for the student, an almost blank screen.
• for the teacher, no clue as to what is going on. (I just found this the hard way. It took me ages, under pressure, to spot the problem.)

Expected result:

• for the student: some sort of polite message when they try to go into the course.
• for the teacher, possibly, some sort of on-screen message when they are in the course/activity, and it is in this bad state. (But that might not be necessary if the message to students is clear enough.)