The JS code should detect it and cope with a reasonable error or default if the API server returns a bad response.

There are two scenarios that need to be, in general, handled gracefully, and that are not right now.

One is if the API server doesn't handle the request at all. This generally passes without notice, except for error messages in the console, but this is almost by accident instead of design. Proper error handling needs to be added.

Second, if the API server has an internal error, it will return an appropriately sized nil set response. The front end needs to detect when it gets nils instead of data that it was expecting, and cope in a reasonable way.