Weird default filter in participants page when group mode is visible groups but no groups created

Setup

1. Access as admin.
2. Create a course with group mode = "visible groups".
3. Enrol some students.
4. DO NOT CREATE ANY GROUPS.

Testing scenario 1

1. Access as student to the course.
2. Go to participants page.
   • CHECK that there isn't any "2:0" default filter.

Testing scenario 2

1. Access as admin or teacher
2. Create a group named "XXXX"
3. Add some students to this group.
4. Access as student to the course.
5. Go to participants page.
   • CHECK that there is a "Group: XXXX" filter and only the participants of this group are displayed.