Menus: Fix `_wp_expand_nav_menu_post_data()` for PHP 5.2.

[37748] introduced `_wp_expand_nav_menu_post_data()` together with an `array_replace_recursive()` compatibility function for PHP 5.2.
Even though that compat function is tried and tested in other projects like BuddyPress, we need to add additional `isset()` checks in order to avoid 'Undefined index' notices in our case.

See #36590.
Built from https://develop.svn.wordpress.org/trunk@37750


git-svn-id: http://core.svn.wordpress.org/trunk@37715 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/compat.php

@@ -471,7 +471,10 @@ if ( ! function_exists( 'array_replace_recursive' ) ) :
 				unset( $bref_stack[ key( $bref_stack ) ] );
 
 				foreach ( array_keys( $head ) as $key ) {
-					if ( isset( $key, $bref ) && is_array( $bref[ $key ] ) && is_array( $head[ $key ] ) ) {
+					if ( isset( $key, $bref ) &&
+					     isset( $bref[ $key ] ) && is_array( $bref[ $key ] ) &&
+					     isset( $head[ $key ] ) && is_array( $head[ $key ] )
+					) {
 						$bref_stack[] = &$bref[ $key ];
 						$head_stack[] = $head[ $key ];
 					} else {

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.6-alpha-37749';
+$wp_version = '4.6-alpha-37750';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.