8336080: Fix -Wzero-as-null-pointer-constant warnings in ClassLoaderStats ctor

Reviewed-by: dholmes, iwalulya

Author: Kim Barrett

src/hotspot/share/classfile/classLoaderStats.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2014, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -82,9 +82,9 @@ class ClassLoaderStats : public ResourceObj {
   uintx             _hidden_classes_count;
 
   ClassLoaderStats() :
-    _cld(0),
-    _class_loader(0),
-    _parent(0),
+    _cld(nullptr),
+    _class_loader(),
+    _parent(),
     _chunk_sz(0),
     _block_sz(0),
     _classes_count(0),