message: Do not send null body in fetch Response
  Fails in Firefox.
diff: @@ -18,7 +18,7 @@ export function jsonapiResponse(_options, body) {
  options.headers['Content-Type'] = 'application/vnd.api+json';
  response = new self.Response(JSON.stringify(body), options);
  } else {
  - response = new self.Response(null, options);
  + response = new self.Response(options);
  }
  // console.log('jsonapiResponse', body, options, response.headers.get('Content-Type'));
  