Cannot acces private property DLM_Download::$id

Hi,

I use this function to limit access to some files:

function dlm_all_downloads_members_only( $can_download, $download ) {
	// No need for checking if access is already denied
	if ( false == $can_download ) {
		return $can_download;
	}

 	if ( ! has_term( 'autres', 'dlm_download_category', $download->id ) ) {
		// Check if user is logged in
		if ( ! is_user_logged_in() ) {
		$can_download = false;
		} // Check if it's a multisite and if user is member of blog
		else if ( is_multisite() && ! is_user_member_of_blog( get_current_user_id(), get_current_blog_id() ) ) {
		$can_download = false;
		}
	}
	else {
		$can_download = true;
	}

	return $can_download;
}

add_filter( 'dlm_can_download', 'dlm_all_downloads_members_only', 10, 2 );

Now, I have this error

PHP Fatal error: Uncaught Error: Cannot access private property DLM_Download::$id

for the line with $download->id.

What can I do?

Thanks.