Async catalog API middleware breaks error handling

[lauraseidler]

With the changes introduced in #390, the catalog API middleware became async. While this works generally fine, it breaks the default express error handling - instead of invoking the next error handler, this will only cause an UnhandledPromiseRejectionWarning, and cause the request to hang and never return an error.

This can be reproduced e.g. by calling /api/catalog/anindexthatdoesnotexist/product/_search.

Wrapping the async middleware in an error handler would be required here - either custom built or using something like https://www.npmjs.com/package/express-async-handler.