WP_Nav_Menu_Widget::widget( array $args, array $instance )

	public function widget( $args, $instance ) {
		// Get menu
		$nav_menu = ! empty( $instance['nav_menu'] ) ? wp_get_nav_menu_object( $instance['nav_menu'] ) : false;

		if ( ! $nav_menu ) {
			return;
		}

		$title = ! empty( $instance['title'] ) ? $instance['title'] : '';

		/** This filter is documented in wp-includes/widgets/class-wp-widget-pages.php */
		$title = apply_filters( 'widget_title', $title, $instance, $this->id_base );

		echo $args['before_widget'];

		if ( $title ) {
			echo $args['before_title'] . $title . $args['after_title'];
		}

		$nav_menu_args = array(
			'fallback_cb' => '',
			'menu'        => $nav_menu
		);

		/**
		 * Filters the arguments for the Navigation Menu widget.
		 *
		 * @since WP-4.2.0
		 * @since WP-4.4.0 Added the `$instance` parameter.
		 *
		 * @param array    $nav_menu_args {
		 *     An array of arguments passed to wp_nav_menu() to retrieve a navigation menu.
		 *
		 *     @type callable|bool $fallback_cb Callback to fire if the menu doesn't exist. Default empty.
		 *     @type mixed         $menu        Menu ID, slug, or name.
		 * }
		 * @param WP_Term  $nav_menu      Nav menu object for the current menu.
		 * @param array    $args          Display arguments for the current widget.
		 * @param array    $instance      Array of settings for the current widget.
		 */
		wp_nav_menu( apply_filters( 'widget_nav_menu_args', $nav_menu_args, $nav_menu, $args, $instance ) );

		echo $args['after_widget'];
	}