8260236: better init AnnotationCollector _contended_group

Reviewed-by: coleenp, shade

Author: MBaesken

src/hotspot/share/classfile/classFileParser.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2021, 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
@@ -1101,7 +1101,7 @@ class AnnotationCollector : public ResourceObj{
   u2 _contended_group;
 
   AnnotationCollector(Location location)
-    : _location(location), _annotations_present(0)
+    : _location(location), _annotations_present(0), _contended_group(0)
   {
     assert((int)_annotation_LIMIT <= (int)sizeof(_annotations_present) * BitsPerByte, "");
   }