attachement default no link

functions.php

<?php

add_action( 'admin_init', 'fs_imagelink_setup', 10 );
/**
 * Set default link option for attachments
 *
 * @return void
 */
function fs_imagelink_setup() {
  $image_set = get_option( 'image_default_link_type' );

	if ( $image_set !== 'none' ) {
		update_option( 'image_default_link_type', 'none' );
	}
}