Programming exercise: error messages when complaints are not visible

[pogobanane]

Describe the bug

When trying to access complaints submitted by students, we get the following error message:
(url: https://artemis.ase.in.tum.de/course-management/276/programming-exercises/14492/submissions/8931574/assessment?correction-round=0)

This error is misleading because, in our case, the errors are thrown because the excercises "Run Tests after Due Date" is set to a point in the future. The complaint is not made accessible yet, because the results may be overridden in the future, once the due date passes and tests are triggered again. The error message does not reflect this though.

To Reproduce

1. Create exam programming exercise with "Run Tests after Due Date" set to a point far in the future. (not too far though, the date picker only sets days and months, but not years)
   

2. Conduct exam

3. Student submits a complaint during the complaint period

4. Instructor goes to the assesment dashboard, starts "Start manual assesment" to resolve the complaint

5. Instructor attempts to open complaint
   

6. See error

Expected behavior

Improve error message: report that results are not visible because due date has not passed yet.

Screenshots

No response

Which version of Artemis are you seeing the problem on?

7.5.6

What browsers are you seeing the problem on?

Firefox

Additional context

No response

Relevant log output

No response