Breadcrumbs on 404 page broken

When breadcrumbs are enabled the 404 page throws an error. The prepare_item function call should be diagnoseo_prepare_item. This fixed it for me. Thanks.

} elseif ( is_404() ) {
echo wp_kses( prepare_item( esc_html__( ‘Error 404 – Not Found.’, ‘diagnoseo’ ) ), $allowed );