WP_Nav_Menu_Widget::form

	 *
	 * @since 3.0.0
	 *
	 * @param array $new_instance New settings for this instance as input by the user via
	 *                            WP_Widget::form().
	 * @param array $old_instance Old settings for this instance.
	 * @return array Updated settings to save.
	 */
	public function update( $new_instance, $old_instance ) {
		$instance = array();
		if ( ! empty( $new_instance['title'] ) ) {
			$instance['title'] = sanitize_text_field( $new_instance['title'] );
		}
		if ( ! empty( $new_instance['nav_menu'] ) ) {
			$instance['nav_menu'] = (int) $new_instance['nav_menu'];
		}
		return $instance;
	}

	/**
	 * Outputs the settings form for the Navigation Menu widget.
	 *
	 * @since 3.0.0
	 *
	 * @param array $instance Current settings.
	 * @global WP_Customize_Manager $wp_customize
	 */
	public function form( $instance ) {
		global $wp_customize;
		$title    = isset( $instance['title'] ) ? $instance['title'] : '';
		$nav_menu = isset( $instance['nav_menu'] ) ? $instance['nav_menu'] : '';

		// Get menus.
		$menus = wp_get_nav_menus();

		$empty_menus_style     = '';
		$not_empty_menus_style = '';
		if ( empty( $menus ) ) {
			$empty_menus_style = ' style="display:none" ';
		} else {
			$not_empty_menus_style = ' style="display:none" ';
		}

		$nav_menu_style = '';
		if ( ! $nav_menu ) {
			$nav_menu_style = 'display: none;';
		}

		// If no menus exists, direct the user to go and create some.
		?>
		<p class="nav-menu-widget-no-menus-message" <?php echo $not_empty_menus_style; ?>>
			<?php
			if ( $wp_customize instanceof WP_Customize_Manager ) {
				$url = 'javascript: wp.customize.panel( "nav_menus" ).focus();';
			} else {
				$url = admin_url( 'nav-menus.php' );
			}

			/* translators: %s: URL to create a new menu. */