Merge pull request #4902 from pine3ree/patch-15

add missing property $user_group_id;

upload/system/library/cart/user.php

@@ -2,6 +2,7 @@
 namespace Cart;
 class User {
 	private $user_id;
+	private $user_group_id;
 	private $username;
 	private $permission = array();