[Sentry reported an error](https://ligo-caltech.sentry.io/issues/5081076463/?alert_rule_id=710526&alert_timestamp=1710797810690&alert_type=email&environment=test&notification_uuid=b5bfedba-abe7-4d31-b25f-280fa8935ba7&project=1456379&referrer=alert_email) in [`core.http.check_and_serve_file`](https://git.ligo.org/computing/gracedb/server/-/blob/bebc24500045d00fc74ba56818bd9b34e184c310/gracedb/core/http.py#L62). The issue is that there's no `else` clause, and `response` is undefined. I don't know of a way to get more details behind this _instance_ of the error, however, there's only one possibility I see triggering this: `file_path` refers to a directory. This would be solved by adding a simple `else` clause to catch all possible remaining errors, though we should probably identify exactly what happened here and see if it needs special treatment. Why did a user try accessing a file that was actually directory, assuming my assessment is correct?