1. Take a course with at least one user and a quiz he did not attempt already.

2. When trying to access the results grades of that quiz, with the option "enrolled users how have not attempt the quiz", the fallowing error message appears:

Coding error detected, it must be fixed by a programmer: Unknown quiz attempt state.

Stack trace:

line 846 of \mod\quiz\locallib.php: coding_exception thrown
line 516 of \mod\quiz\attemptlib.php: call to quiz_attempt_state_name()
line 155 of \mod\quiz\report\attemptsreport_table.php: call to quiz_attempt::state_name()
line 703 of \lib\tablelib.php: call to quiz_attempts_report_table->col_state()
line 1271 of \lib\tablelib.php: call to flexible_table->format_row()
line 66 of \mod\quiz\report\overview\overview_table.php: call to table_sql->build_table()
line 1383 of \lib\tablelib.php: call to quiz_overview_table->build_table()
line 236 of \mod\quiz\report\overview\report.php: call to table_sql->out()
line 100 of \mod\quiz\report.php: call to quiz_overview_report->display()