if ($_key != '') {
                    if (!isset($this->tpl_vars[$_key])) {
                        $tpl_var_inst = $this->getVariable($_key, null, true, false);
                        if ($tpl_var_inst instanceof Undefined_Smarty_Variable) {
                            $this->tpl_vars[$_key] = new Smarty_variable(null, $nocache);