8337840: Remove redundant null check in ObjectOutputStream.writeProxyDesc

Reviewed-by: rriggs

Author: Andrey Turbanov

src/java.base/share/classes/java/io/ObjectOutputStream.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1996, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1996, 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
@@ -1272,7 +1272,7 @@ private void writeProxyDesc(ObjectStreamClass desc, boolean unshared)
         }
 
         bout.setBlockDataMode(true);
-        if (cl != null && isCustomSubclass()) {
+        if (isCustomSubclass()) {
             ReflectUtil.checkPackageAccess(cl);
         }
         annotateProxyClass(cl);