Fix errors

###### Fixed:
```
test/functional/grade_entry_forms_controller_test.rb (20 errors)
test/functional/groups_controller_test.rb (1 error)
test/functional/marks_graders_controller_test.rb (3 errors)
test/functional/notes_controller_test.rb (18 errors)
test/functional/main_controller_test.rb (12 errors)
test/functional/role_switching_test.rb (2 failures)
test/functional/groups_controller_csv_upload_test.rb (2 failures)
test/functional/submissions_controller_test.rb (1 warning)
test/functional/results_controller_test.rb (4 errors)
```
###### TODO:
```
test/functional/automated_tests_controller_test.rb (13 tests, 12 assertions, 5 failures, 2 errors, 0 skips)
test/unit/helpers/ensure_config_helper_test.rb (9 tests, 5 assertions, 0 failures, 1 errors, 0 skips)
test/unit/markus_logger_test.rb (20 tests, 20 assertions, 1 failures, 0 errors, 0 skips)
test/unit/submission_collector_test.rb (16 tests, 50 assertions, 1 failures, 0 errors, 0 skips)
spec/models/grade_entry_student_spec.rb (12 examples, 1 failure)
spec/controllers/groups_controller_spec.rb (16 examples, 3 failures)
```
Redundant `return` detected.