mPDF不需要的filenameoutput或标头

I try to use another css for mpdf generating as my template is using on direct screen showing. For this I removed the HTML-Header from $mpdf and set my css directly in the mPDF call:

$mpdf->WriteHTML($stylesheet,1);
$mpdf->WriteHTML($html, 2);

But with this I got an unwanted filenameoutput on my PDF. I think this is adding a header on my page.

How can I remove this filenameoutput?

Here is my complete mPDF-function call:

function mpdfInvoice($pdfname){
    require_once __DIR__ . '/vendor/autoload.php';

    $defaultConfig = (new Mpdf\Config\ConfigVariables())->getDefaults();
    $fontDirs = $defaultConfig['fontDir'];

    $defaultFontConfig = (new Mpdf\Config\FontVariables())->getDefaults();
    $fontData = $defaultFontConfig['fontdata'];

    $mpdf = new \Mpdf\Mpdf([
        'fontDir' => array_merge($fontDirs, [
            __DIR__ . '/fonts',
        ]),
        'fontdata' => $fontData + [
            'nunito' => [
                'R' => 'nunito-regular.ttf',
                'B' => 'nunito-bold.ttf',
            ]
        ],
        'default_font' => 'nunito',
        'mode' => 'utf-8',
        'orientation' => 'P',
        // 'mode' => 'c',
    ]);

    $stylesheet = file_get_contents('assets/css/invoice_mpdf.css');

    $mpdf->shrink_tables_to_fit = 0;


    $url = url('/validation-registration/' . $pdfname);
    $html = file_get_contents($url);

    $mpdf->WriteHTML($stylesheet,1);
    $mpdf->WriteHTML($html, 2);

    $mpdf->Output('content/validation-registration/' .  $pdfname . '/' . $pdfname . '.pdf', 'F');
}

Cheers