This is a very minor issue as the code in messagelib.php adds the missing fields after the debugging message:

Necessary properties missing in userto object, fetching full record
line 95 of /lib/messagelib.php: call to debugging()
line 1453 of /mod/quiz/locallib.php: call to message_send()
line 1534 of /mod/quiz/locallib.php: call to quiz_send_notification()
line 1649 of /mod/quiz/locallib.php: call to quiz_send_notification_messages()
line ? of unknownfile: call to quiz_attempt_submitted_handler()
line 155 of /lib/classes/event/manager.php: call to call_user_func()
line 89 of /lib/classes/event/manager.php: call to core\event\manager::process_buffers()
line 2411 of /lib/dml/moodle_database.php: call to core\event\manager::database_transaction_commited()
line 92 of /lib/dml/moodle_transaction.php: call to moodle_database->commit_delegated_transaction()
line 184 of /mod/quiz/processattempt.php: call to moodle_transaction->allow_commit()

FIX
mod/quiz/locallib.php #1486

— $notifyfields = 'u.id, u.username, u.idnumber, u.email, u.emailstop, u.lang, u.timezone, u.mailformat, u.maildisplay, ';
+++ $notifyfields = 'u.id, u.username, u.idnumber, u.email, u.emailstop, u.lang, u.timezone, u.mailformat, u.maildisplay, u.auth, u.suspended, u.deleted,';