We were attempting to add course overrides twice to objects returned in
the toggle state report view. This was causing a TypeError (and thus a
500 error) because the second time, we were attempting to add entries to
an incorrect object.
This issue was not caught by unit tests because we were not testing the
view with WaffleFlagCourseOverride objects. This commit adds a unit test
to prevent future errors.
This is another fix for PR #27108.
dae4403ba7