_whois_cleanup_address should use "error" for drupal_set_message "type"

If a bad domain name is entered by the user, the function _whois_cleanup_address() currently calls drupal_set_message() as follows:

if (!empty($address) && empty($result['domain'])) {
    drupal_set_message(t("Invalid address received."));
  }

As this is an error condition, this should be:

if (!empty($address) && empty($result['domain'])) {
    drupal_set_message(t("Invalid address received."), 'error');
  }