// delete all empty Categories
$acSql = "select s_categories.id from s_categories left join s_articles_categories_ro ro on ro.categoryID = s_categories.id where ro.id IS NULL and s_categories.parent is not null and s_categories.blog=false and s_categories.path is not null";
$categoryIds = Shopware()->Db()->fetchAll($acSql);
foreach($categoryIds as $catId){
  try {
    $this->getCategoryResource()->delete($catId['id']);
  }catch(\Exception $e){
    //do nothing
  }
}