bbp_get_topic_id function not exist

[devhaozi]

I use WordPress multisite and only activate bbPress on one site. When I use this plugin, The sites without activate bbPress will throw a PHP error bbp_get_topic_id function not exist around file class-bbpress.php line 492.

I suggest adding a judge to fix this:

if ( ! function_exists( 'bbp_get_topic_id' ) ) {
    return [];
}

The modified complete function is as follows:

    public function get_topic_users( $topic_id = 0 ) {
        if ( ! function_exists( 'bbp_get_topic_id' ) ) {
            return [];
        }
        $topic_id = bbp_get_topic_id( $topic_id );
        if ( empty( $topic_id ) ) {
            return [];
        }

        $user_id = bbp_get_topic_author_id( $topic_id );
        $users = [ $user_id ];
        $users_formatted = [ $this->get_user_data( $user_id, $topic_id ) ];

        // Get an array of replies for the topic
        $replies = get_posts(
            [
                'fields'      => 'ids',
                'numberposts' => 100,
                'post_parent' => $topic_id,
                'post_type'   => bbp_get_reply_post_type(),
                'post_status' => bbp_get_public_status_id(),
            ]
        );

        // Loop through the replies and get the user IDs
        foreach ( $replies as $reply_id ) {
            $user_id = bbp_get_reply_author_id( $reply_id );
            // Add the user ID to the array if it's not already there
            if ( ! in_array( $user_id, $users ) ) {
                $users[] = $user_id;
                $users_formatted[] = $this->get_user_data( $user_id, $reply_id );
            }
        }

        return $users_formatted;
    }