function my_wpforms_filter( $update_data, $user_id, $contact_id ) {

    if( ! is_user_logged_in() && ! empty( $contact_id ) ) {
        $update_data = array();
    }

    return $update_data;

}

add_filter( 'wpf_wpforms_pre_submission', 'my_wpforms_filter', 10, 3 );