Topic title in <title> tag, for group forum topic

<?php
add_filter( 'bp_get_title_parts', 'boss_child_wp_title', 20 );
/**
 * Add the topic title part into <title> tag, when viewing a topic in group forums.
 *
 * @global type $wpdb
 * @param array $title_parts
 * @return array
 */
function boss_child_wp_title( $title_parts ){
    if( function_exists( 'bbp_get_topic_post_type' ) && function_exists( 'bp_is_group_forum_topic' ) && bp_is_group_forum_topic() ){
        $topic_slug = bp_action_variable( 1 );
        if( empty( $topic_slug ) )
            return $title_parts;

        //$topic = get_page_by_path( $topic_slug, OBJECT, bbp_get_topic_post_type() );

        global $wpdb;
        $topic_title = $wpdb->get_var( $wpdb->prepare(
            "SELECT post_title FROM {$wpdb->posts} WHERE post_type=%s AND post_name=%s",
            bbp_get_topic_post_type(),
            $topic_slug
        ) );

        if( empty( $topic_title ) || is_wp_error( $topic_title ) )
            return $title_parts;

        //$topic_title = wp_trim_words( $topic_title, 10 );//limit it to 10 words
        $new_parts = array( $topic_title );
        if( !empty( $title_parts ) ){
            foreach( $title_parts as $p ){
                $new_parts[] = $p;
            }
        }

        $title_parts = $new_parts;
    }
    return $title_parts;
}