I'd still like to simplify the logic in this callback, whether in this pull request or later. For example, as it stands it seems like if the underlying method called the callback with `(null, null)`, `data` would become `{message: DEFAULT_ERROR}` and yet we would call `next()` as if the call was successful. At least writing out tests for the various cases we expect to encounter would help clarify all the combinations we're trying to account for I guess.