WordPress Debug log notice

Hi
My debug.log is full of:

PHP Notice: AMP_Post_Template::get est appelée de la mauvaise manière. Called for non-existant key (“font_urls”). Veuillez lire Débugger dans WordPress (en) pour plus d’informations. (Ce message a été ajouté à la version 0.1.) in /home/domofr/public_html/wp-includes/functions.php on line 4136

The only things related to fonts is in my functions.php:

add_action( 'amp_post_template_head', 'xyz_amp_add_head' );
function xyz_amp_add_head( $amp_template ) {
    ?>
<!-- <p>AJOUT DANS HEADER</p> -->
<link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Quicksand">
<link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Raleway:300">
<script async custom-element="amp-social-share" src="https://cdn.ampproject.org/v0/amp-social-share-0.1.js"></script>
<script async custom-element="amp-fit-text" src="https://cdn.ampproject.org/v0/amp-fit-text-0.1.js"></script>
<script async custom-element="amp-sidebar" src="https://cdn.ampproject.org/v0/amp-sidebar-0.1.js"></script>

    <?php
}

What’s wrong?

Thanks