repository settings page does not display errors properly

Created by: slimsag

The repository settings page does not display errors properly: https://sourcegraph.com/github.com/sourcegraph/sourcegraph/-/settings

When the GraphQL endpoints on this page return errors, the page just shows an error:

If you want to reproduce this, remove the repo-updater line in your dev Procfile (repo-updater being down is how I and multiple customers ran into this).

Reported by https://app.hubspot.com/contacts/2762526/company/561806411 and https://app.hubspot.com/contacts/2762526/company/407948923

See #3594 (closed) for details (ctrl+f on that page for this issue #)