From 62de6cc7ecf42c2c68f99ce63ed0c6783ca81aee Mon Sep 17 00:00:00 2001
From: Peter Wilson <wilson@peterwilson.cc>
Date: Sun, 14 May 2017 03:38:48 +0000
Subject: [PATCH] Menus: Prevent empty class attribute following [40537].

Prevents an empty class attribute, `class=""`, from appearing in the HTML if a developer removes all classes using the `nav_menu_submenu_css_class` filter.

Props Kopepasah.
Fixes #36163.

Built from https://develop.svn.wordpress.org/trunk@40665


git-svn-id: http://core.svn.wordpress.org/trunk@40528 1a063a9b-81f0-0310-95a4-ce76da25c4cd
---
 wp-includes/class-walker-nav-menu.php | 11 ++++++-----
 wp-includes/version.php               |  2 +-
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/wp-includes/class-walker-nav-menu.php b/wp-includes/class-walker-nav-menu.php
index c97188b473..83dbfed45c 100644
--- a/wp-includes/class-walker-nav-menu.php
+++ b/wp-includes/class-walker-nav-menu.php
@@ -59,6 +59,9 @@ class Walker_Nav_Menu extends Walker {
 		}
 		$indent = str_repeat( $t, $depth );
 
+		// Default class.
+		$classes = array( 'sub-menu' );
+
 		/**
 		 * Filters the CSS class(es) applied to a menu list element.
 		 *
@@ -68,12 +71,10 @@ class Walker_Nav_Menu extends Walker {
 		 * @param stdClass $args    An object of `wp_nav_menu()` arguments.
 		 * @param int      $depth   Depth of menu item. Used for padding.
 		 */
+		$class_names = join( ' ', apply_filters( 'nav_menu_submenu_css_class', $classes, $args, $depth ) );
+		$class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';
 
-		$classes = array( 'sub-menu' );
-		$classes = apply_filters( 'nav_menu_submenu_css_class', $classes, $args, $depth );
-		$class_names = join( ' ', $classes );
-
-		$output .= "{$n}{$indent}<ul class='" . esc_attr( $class_names ) . "'>{$n}";
+		$output .= "{$n}{$indent}<ul $class_names>{$n}";
 	}
 
 	/**
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 15e073f7ae..c25834cc33 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.8-beta1-40664';
+$wp_version = '4.8-beta1-40665';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.