Bug "Undefined variable: options"

There is a bug for the var `$option`:

    Notice: Undefined variable: options in [...]/vendor/phpoffice/phpexcel/Classes/PHPExcel/Settings.php on line 384

This bug is fixed with `self::$_libXmlLoaderOptions == (LIBXML_DTDLOAD | LIBXML_DTDATTR)` instead of `$options == (LIBXML_DTDLOAD | LIBXML_DTDATTR)`