critical error after select child theme

Here i am having problems: https://redspot.es/wp-admin/themes.php this:

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When i have created a functions.php for the twenty twenty five child theme that i am writing and that has this content:

<?php
/**
 * Twenty Twenty-Five child functions and definitions.
 *
 * @link https://developer.wordpress.org/themes/basics/theme-functions/
 *
 * @package WordPress
 * @subpackage Twenty_Twenty_Five child
 * @since Twenty Twenty-Five 1.0
 */
// Añadir la imagen destacada antes del extracto
add_filter('the_excerpt''mostrar_imagen_destacada_en_extracto');
function mostrar_imagen_destacada_en_extracto($excerpt) {
    if (has_post_thumbnail()) {
        $img = get_the_post_thumbnail(get_the_ID()'thumbnail');
        $excerpt = $img . $excerpt;
    }
    return $excerpt;
}

Where is the problem?

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