Error Log OpenCart 1.5.5.1 shows catalog/controller/module/category_superfish.php on line 81

Error Log OpenCart 1.5.5.1 shows catalog/controller/module/category_superfish.php on line 81

    Line 81:
    if($query->row['parent_id']==0) $this->parent_id = $category_id;


    Any suggestions greatly appreciated.