Triggering a fatal error in an adhoc task is bad. It will be retried indefinitely.
Even though we are not sure how to get a module instance without a course module record,
it is possible and should not kill the Moodle site.
Previously we did not require the lib.php files for each module
in this ad-hoc task, which meant that the *_refresh_events functions
would only be called if some lucky sequence of events led to the
lib.php file for the module being required.
Instead we should use the component_callback function which can handle
that stuff automagically.
Damyon Wiese