function hook_preprocess_html(&$variables)
{
  $variables['page_top'] = NULL;
  if (isset($variables['html']['page_top'])) {
    $variables['page_top'] = $variables['html']['page_top'];
    unset($variables['html']['page_top']);
  }
  $variables['page_bottom'] = NULL;
  if (isset($variables['html']['page_bottom'])) {
    $variables['page_bottom'] = $variables['html']['page_bottom'];
    unset($variables['html']['page_bottom']);
  }
}