Drupal: Add Body Class when Tabs are displayed

template.php

<?php
function THEMENAME_preprocess_html(&$vars, $hook) {
  // Make tabs available on html tpl
  $vars['tabs'] = menu_local_tabs();
  // if we have primary tabs, add an accoring body class
  if (!empty($vars['tabs']['#primary'])) {
    $vars['classes_array'][] = 'has-tabs';
  }
}