我开发了一个小部件来显示最新消息。小部件功能正常工作，但问题是小部件标题未保存在后端。正确的方法是什么？

class infotravel_news_list_widget extends WP_Widget {
    public function __construct() {
        parent::__construct( false, $name = __( \'Latest News\', \'infotravel\' ) );
    }

    public function form( $instance ) {

        $defaults = array(
                \'title\' => \'\',
        );

        extract( wp_parse_args( array( $instance, $defaults ) ) );

        // Widget title ?>
        <p>
            <label for="<?php echo esc_attr( $this->get_field_id( \'title\' ) ); ?>"><?php _e( \'Title\', \'infotravel\' ); ?></label>
            <input class="widefat" id="<?php echo esc_attr( $this->get_field_id( \'title\' ) ); ?>" name="<?php echo esc_attr( $this->get_field_name( \'title\' ) ); ?>" type="text" value="<?php echo esc_attr( $defaults[\'title\'] ); ?>" />
        </p>

        <?php
    }

    public function update( $new_instance, $old_instance ) {
        $instance = $old_instance;
        $instance[\'title\'] = isset( $new_instance[\'title\'] ) ? wp_strip_all_tags( $new_instance[\'title\'] ) : \'\';

        return $instance;
    }

    public function widget( $args, $instance ) {
        $news_args = array(
            \'post_type\'      => \'infotravel_news\',
            \'posts_per_page\' => 5,
            \'post_status\'    => \'publish\',
            \'orderby\'        => \'post_date\',
            \'order\'          => \'desc\'
        );
        $query = new WP_Query( $news_args );

        if( $query -> have_posts() ) :
            while( $query -> have_posts() ) : $query -> the_post(); ?>
                <h3><?php the_title(); ?></h3>
            <?php
            endwhile;
        endif;
    ?>

    <?php }
}

add_action( \'widgets_init\', function(){
    register_widget( \'infotravel_news_list_widget\' );
} );