found on all local and MIT stable instances
Steps to reproduce:
1. Publish an assessment with the "graders can see student's identities" setting on.
2. Create an account with a username, but no first name or last name field.
3. Take the assessment as that user and submit it for grading
4. View the Total Scores for the assessment. The user will be listed as "Anonymous", and you can click on that to get to the student scores page.
5. View the Question Scores page for the assessment. The user will not have any submission ID or name link at all - you can't get to student scores for that user.
Fix: Entries for users with no fullname fields in the question scores page should at least say "Anonymous". It'd be even better if we could use the userid instead, as there might be several "Anonymous"es taking a test.