RFR: 8337243: Fix more -Wzero-as-null-pointer-constant warnings in compiler code [v2]

[Kim Barrett]

On Fri, 26 Jul 2024 05:38:59 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

>> Kim Barrett has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   remove extraneous whitespace
>
> Marked as reviewed by vlivanov (Reviewer).

Thanks for reviews @iwanowww and @vnkozlov .

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PR Comment: https://git.openjdk.org/jdk/pull/20343#issuecomment-2253011486