RFR: 8335588: Fix -Wzero-as-null-pointer-constant warnings in calls to Node ctor

[Christian Hagedorn]

On Wed, 3 Jul 2024 02:38:59 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

> Please review this change to callers of the Node constructor that were passing
> 0 as the first argument, which is of type Node*, thereby triggering
> -Wzero-as-null-pointer-constant warnings when enabled. Instead of 0, pass
> nullptr.  This removes over 2K warnings when building with that option.
> 
> Testing: mach5 tier1

Looks good to me, too.

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Marked as reviewed by chagedorn (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/19994#pullrequestreview-2155595930