We recently got the first request for personal data according to to the GDPR. After one issue was solved by the update to 3.4.7 (missing categories prevented processing of the request), we encountered another problem. Every time such a request was processed the admin user got an error message:

Ausnahme beim Aufruf von CORE_COURSE\PRIVACY\PROVIDER::EXPORT_USER_DATA.
Das Plugin CORE_COURSE konnte die Verarbeitung der Daten nicht beenden.
Unten finden Sie Informationen für den PluginentwicklerReturn value of core_completion\privacy\provider::get_course_completion_info() must be of the type array, none returned#0 /srv/moodle/course/classes/privacy/provider.php(115): core_completion\privacy\provider::get_course_completion_info(Object(stdClass), Object(stdClass))
#1 /srv/moodle/lib/moodlelib.php(7781): core_course\privacy\provider::export_user_data(Object(core_privacy\local\request\approved_contextlist))
#2 /srv/moodle/privacy/classes/manager.php(578): component_class_callback('core_course
pri...', 'export_user_dat...', Array)
#3 /srv/moodle/privacy/classes/manager.php(611): core_privacy\manager::component_class_callback('core_course', 'core_privacy
lo...', 'export_user_dat...', Array)
#4 /srv/moodle/privacy/classes/manager.php(339): core_privacy\manager->handled_component_class_callback('core_course', 'core_privacy
lo...', 'export_user_dat...', Array)
#5 /srv/moodle/admin/tool/dataprivacy/classes/task/process_data_request_task.php(107): core_privacy\manager->export_user_data(Object(core_privacy\local\request\contextlist_collection))
#6 /srv/moodle/lib/cronlib.php(185): tool_dataprivacy\task\process_data_request_task->execute()
#7 /srv/moodle/lib/cronlib.php(74): cron_run_inner_adhoc_task(Object(tool_dataprivacy\task\process_data_request_task))
#8 /srv/moodle/admin/cli/cron.php(61): cron_run()
#9 {main}

The data request itself seems to be completed anyway. Probably missing the course completion status.