It looks like there's an error when a user is suspended. My cronjob keeps failing with these messages:

Execute adhoc task: mod_assign\task\queue_assignment_due_soon_notification_tasks_for_users
Adhoc task id: 5207306
Adhoc task custom data: {"id":"86881"}
... started 08:42:27. Current memory use 19.1 MB.
... used 608 dbqueries
... used 0.58336806297302 seconds
Adhoc task failed: mod_assign\task\queue_assignment_due_soon_notification_tasks_for_users,Suspended account
Backtrace:

• line 249 of /lib/classes/task/manager.php: call to core\user::require_active_user()
• line 45 of /mod/assign/classes/task/queue_assignment_due_soon_notification_tasks_for_users.php: call to core\task\manager::queue_adhoc_task()
• line 519 of /lib/classes/cron.php: call to mod_assign\task\queue_assignment_due_soon_notification_tasks_for_users->execute()
• line 302 of /lib/classes/cron.php: call to core\cron::run_inner_adhoc_task()
• line 128 of /lib/classes/cron.php: call to core\cron::run_adhoc_tasks()
• line 186 of /admin/cli/cron.php: call to core\cron::run_main_process()