As sent to the moodle.org privacy officer:

Exception occurred while calling core_backup\privacy\provider::delete_data_for_user.
This means that plugin core_backup did not complete the processing of data. The following exception information may be passed on to the plugin developer:
Call to a member function get_userids() on null

#0 [internal function]: core_backup\privacy\provider::delete_data_for_user(Object(core_privacy\local\request\approved_contextlist))
#1 /opt/app/lib/moodlelib.php(8000): call_user_func_array('core_backup
pri...', Array)
#2 /opt/app/privacy/classes/manager.php(578): component_class_callback('core_backup
pri...', 'delete_data_for...', Array)
#3 /opt/app/privacy/classes/manager.php(611): core_privacy\manager::component_class_callback('core_backup', 'core_privacy
lo...', 'delete_data_for...', Array)
#4 /opt/app/privacy/classes/manager.php(415): core_privacy\manager->handled_component_class_callback('core_backup', 'core_privacy
lo...', 'delete_data_for...', Array)
#5 /opt/app/admin/tool/dataprivacy/classes/task/process_data_request_task.php(138): core_privacy\manager->delete_data_for_user(Object(core_privacy\local\request\contextlist_collection))
#6 /opt/app/lib/cronlib.php(341): tool_dataprivacy\task\process_data_request_task->execute()
#7 /opt/app/lib/cronlib.php(198): cron_run_inner_adhoc_task(Object(tool_dataprivacy\task\process_data_request_task))
#8 /opt/app/lib/cronlib.php(76): cron_run_adhoc_tasks(1641997980)
#9 /opt/app/admin/cli/cron.php(178): cron_run()
#10

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