message: Add a null guard for serverConfig
  This is often null while the component is on its first render, and is called during that render. It is eventually populated by React, and the function re-called - we just have to be patient.
diff: @@ -204,7 +204,7 @@ export default React.createClass({
  },
  getFallbackHsUrl: function() {
  - if (this.props.serverConfig.isDefault) {
  + if (this.props.serverConfig && this.props.serverConfig.isDefault) {
  return this.props.config.fallback_hs_url;
  } else {
  return null;
  