The report creates with
moodle/mod/quiz/report.php?mode=overview&id=xxx
is empty. A php error is showed:

Unknown column 'feedback' in 'order clause'
SELECT CONCAT(u.id,'#', IFNULL(qa.attempt, 0) ) AS uniqueid, qa.uniqueid as attemptuniqueid, qa.id AS attempt, u.id AS userid, u.firstname, u.lastname, u.picture, qa.sumgrades, qa.timefinish, qa.timestart, qa.timefinish - qa.timestart AS duration , qf.feedbacktext FROM mdl_user u JOIN mdl_role_assignments ra ON ra.userid = u.id JOIN mdl_groups_members gm ON u.id = gm.userid JOIN mdl_quiz_attempts qa ON u.id = qa.userid AND qa.quiz = 58 JOIN mdl_quiz_feedback AS qf ON qf.quizid = 58 AND qf.mingrade display()