RPKI endpoint returns invalid JSON on some ASNs

For example, when running `curl -6 https://valid.rpki.cloudflare.com/bc66fd0d2` from my [AS198747](https://bgp.he.net/AS198747), the following invalid JSON payload is returned:

```
{"status":"valid", "asn":undefined, "name": "", "blackholed":false}
```

Not quite sure as to why the AS name isn't picked up from the [RIPE database entry](https://apps.db.ripe.net/db-web-ui/lookup?source=ripe&key=AS198747&type=aut-num), but either way that field should contain at least `null` , not `undefined`, as that's invalid JSON that causes a generic error when running the test.

Reproduce the response with curl -6 against https://valid.rpki.cloudflare.com/bc66fd0d2, then trace the RPKI endpoint's response generation for AS198747. Confirm how missing ASN names are represented and verify that the endpoint always returns valid JSON, using the reported payload as the regression case.

Written by the indexing model from the issue text.