message: only start hub if there are data sources
  This was an unintentional regression when we reorganized the directories.
diff: @@ -46,7 +46,7 @@ let addon = {
  async url() {
  if (!this._hub) {
  this._env = process.env.EMBER_ENV || 'development';
  - if (fs.existsSync(path.join(path.dirname(this.project.configPath()), '..', 'cardstack'))) {
  + if (fs.existsSync(path.join(path.dirname(this.project.configPath()), '..', 'cardstack', 'data-sources'))) {
  this._hub = this._startHub();
  } else {
  this._hub = Promise.resolve(null);
  