In the Joomla 4 template Layla, I am trying to integrate the JEvents component. When displaying the calendar, a PHP line warning appears in a template file:

note
: Undefined variable: hornav in
/var/www/webxxx/html/j4ssv1863saydapage/templates/j51_layla/inc/layouts/hornav.php on-line11

LINK: http://j4ssv1863sayda.ssvsayda.de/index.php/termine

Report errors is set to "Maximum" in the server settings. The error comes, but if there is an error, display: none
Mainly the header is destroyed when you click on: "Kalender" or "Termin Eintragen" Enter an appointment"

The code in the file is as follows:

<?php 

defined( '_JEXEC' ) or die( 'Restricted index access' );

 ?>



<?php if($this->params->get('hornavPosition') == '1') : ?>

    <nav id="hornav-nav" class="hornav">

        <jdoc:include type="modules" name="hornav" />

    </nav>

<?php else : ?>

    <nav id="hornav-nav" class="hornav">

        <?php echo $hornav; ?>

    </nav>

<?php endif; ?>