[Escalated to WPML Developers team] Fatal error: wp_delete_file expects string return type you return null - TypeError: is_file() expect...

Background of the issue:
In my theme I need to hook onto WP core "wp_delete_file"
This filter expects a string param and return type:
hidden link

But you return null: wp-contentpluginssitepress-multilingual-cmsclassesmediaclass-wpml-attachment-action.php line 180

<code>
public function delete_file_filter( $file ) {
if ( $file ) {
$file_name = $this->get_file_name( $file );
$scaled_file_name = $this->get_file_name( $file, true );
$sql = "SELECT pm.meta_id, pm.post_id FROM {$this->wpdb->postmeta} AS pm WHERE pm.meta_value IN ( %s, %s ) AND pm.meta_key='_wp_attached_file'";
$attachment_prepared = $this->wpdb->prepare( $sql, $file_name, $scaled_file_name );
$attachment = $this->wpdb->get_row( $attachment_prepared );

if ( ! empty( $attachment ) ) {
$file = null;
}
}

return $file;
}
</code>

Which then leads to a PHP fatal error:
TypeError: is_file() expects parameter 1 to be a valid path, null given

The code in my functions.php

<code>
add_filter('wp_delete_file', function ( $file ) {
if ( ! is_file( $file ) ) {
return $file;
}

// some custom logic

return '';
}, 20);
</code>

I know I can validate $file for null in my code, however that's not the point. Please fix your code to return empty string isntead of null.

Symptoms:
Fatal error: wp_delete_file expects string return type you return null - TypeError: is_file() expects parameter 1 to be a valid path, null given. The code in WPML returns null instead of an empty string, leading to a PHP fatal error.

Questions:
Can you fix your code to return an empty string instead of null