message: Test `defaultServerName` before showing it on forgot password
  The Forgot Password screen wasn't checking the default server name for a value
  before showing it, leading to a possible "Your Matrix account on <blank>"
  message.
  Fixes
diff: @@ -222,7 +222,7 @@ module.exports = React.createClass({
  }
  let yourMatrixAccountText = _t('Your Matrix account');
  - if (this.state.enteredHsUrl === this.props.defaultHsUrl) {
  + if (this.state.enteredHsUrl === this.props.defaultHsUrl && this.props.defaultServerName) {
  yourMatrixAccountText = _t('Your Matrix account on %(serverName)s', {
  serverName: this.props.defaultServerName,
  });
  