If you access EventMetrics with a URL and you are not logged in (don't have a valid session), you receive a fatal error.
Example: https://eventmetrics.wmflabs.org/programs/1/events/47/revisions?format=wikitext
We should catch the user that's not logged in and redirect to / or something that helps the user. Ideally, we'd show a message like, "You must be logged in to see that page, please log in." After logging in, the user would be redirected to the page in the original request.