Multisite mails: Initialize `$current_user` before accessing `$current_user->user_login`.

props Toro_Unit.
see #31217.
fixes #33254.
Built from https://develop.svn.wordpress.org/trunk@33569


git-svn-id: http://core.svn.wordpress.org/trunk@33536 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/ms.php

@@ -298,6 +298,7 @@ All at ###SITENAME###
 	 */
 	$content = apply_filters( 'new_admin_email_content', $email_text, $new_admin_email );
 
+	$current_user = wp_get_current_user();
 	$content = str_replace( '###USERNAME###', $current_user->user_login, $content );
 	$content = str_replace( '###ADMIN_URL###', esc_url( admin_url( 'options.php?adminhash='.$hash ) ), $content );
 	$content = str_replace( '###EMAIL###', $value, $content );

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.3-RC1-33563';
+$wp_version = '4.3-RC1-33569';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.