If there are multichoice questions in the database with no answers (doesn't seem possible from the GUI, but we have a few from past semesters in our database), the recalculate scheduled task throws an exception because the value for randomguessscore is calculated as NAN (in question/type/multichoice/questiontype.php:252, denominator of count of answers is 0, division by 0 error). The exception causes the entire task to fail. Even though it is a remote possibility, should a check for dividing by 0 be included here to prevent the task from failing altogether?

Scheduled task failed: Recalculate question statistics (quiz_statistics\task\recalculate),Error writing to database (Unknown column 'NAN' in 'field list'
Debug info:
Unknown column 'NAN' in 'field list'
INSERT INTO mdl_question_statistics (hashcode,timemodified,questionid,slot,subquestion,s,effectiveweight,negcovar,discriminationindex,discriminativeefficiency,sd,facility,subquestions,maxmark,positions,randomguessscore,variant) VALUES(?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)
[array (
  0 => '67a4aa3ea0c50feb5a90e36dec5271716c86ac33',
  1 => 1681313612,
  2 => '4715684',
  3 => NULL,
  4 => 1,
  5 => 19,
  6 => NULL,
  7 => 0,
  8 => NULL,
  9 => NULL,
  10 => 0.0,
  11 => 0.0,
  12 => '',
  13 => '5.0000000',
  14 => '3,4,7,9,10,11,12,14,15,16,19',
  15 => NAN,
  16 => NULL,
)]
Backtrace:

• line 293 of /lib/dml/moodle_read_slave_trait.php: call to moodle_database->query_end()
• line 1362 of /lib/dml/mysqli_native_moodle_database.php: call to mysqli_native_moodle_database->query_end()
• line 1408 of /lib/dml/mysqli_native_moodle_database.php: call to mysqli_native_moodle_database->insert_record_raw()
• line 231 of /question/classes/statistics/questions/calculated.php: call to mysqli_native_moodle_database->insert_record()
• line 271 of /question/classes/statistics/questions/all_calculated_for_qubaid_condition.php: call to core_question\statistics\questions\calculated->cache()
• line 259 of /question/classes/statistics/questions/calculator.php: call to core_question\statistics\questions\all_calculated_for_qubaid_condition->cache()
• line 650 of /mod/quiz/report/statistics/report.php: call to core_question\statistics\questions\calculator->calculate()
• line 937 of /mod/quiz/report/statistics/report.php: call to quiz_statistics_report->get_all_stats_and_analysis()
• line 108 of /mod/quiz/report/statistics/classes/task/recalculate.php: call to quiz_statistics_report->calculate_questions_stats_for_question_bank()
• line 259 of /lib/cronlib.php: call to quiz_statistics\task\recalculate->execute()
• line 120 of /lib/cronlib.php: call to cron_run_inner_scheduled_task()
• line 73 of /lib/cronlib.php: call to cron_run_scheduled_tasks()
• line 178 of /admin/cli/cron.php: call to cron_run()

Thanks!