mod_assign: Group filter not applied to grading interface participant selector

1) Navigate to an assignment in groups mode 2) Click View all submissions. 3) Choose a group from the separate group dropdown. 4) The list of submissions gets filtered to that group. 5) Click grade for any student. 6) The grading interface pops up. 7) Click the dropdown to select a different student. 8) Notice that the dropdown lists all students, not just the group selected in step 3.