Changing a course event to a user event results in an error

SELECT id,category FROM {course} WHERE id = ?

[array (

  0 => '0',

)]

Error code: invalidrecord

* line 1546 of /lib/dml/moodle_database.php: dml_missing_record_exception thrown

* line 1522 of /lib/dml/moodle_database.php: call to moodle_database->get_record_select()

* line 6556 of /lib/accesslib.php: call to moodle_database->get_record()

* line 304 of /calendar/classes/external/event_exporter_base.php: call to context_course::instance()

* line 69 of /calendar/classes/external/event_exporter.php: call to core_calendar\external\event_exporter_base->get_other_values()

* line 125 of /lib/classes/external/exporter.php: call to core_calendar\external\event_exporter->get_other_values()

* line 948 of /calendar/externallib.php: call to core\external\exporter->export()

* line 228 of /lib/externallib.php: call to core_calendar_external::submit_create_update_form()

* line 59 of /lib/ajax/service.php: call to external_api::call_external_function()

*