function ignore_unknown_tags( $tags ) {

    $available_tags = wp_fusion()->settings->get( 'available_tags' );

    foreach ( $tags as $i => $tag_id ) {
        if ( ! isset( $available_tags[ $tag_id ] ) ) {
            unset( $tags[ $i ] );
        }
    }

    return $tags;

}

add_filter( 'wpf_api_get_tags_result', 'ignore_unknown_tags' );