[jdk21u-dev] RFR: 8350767: Fix -Wzero-as-null-pointer-constant warnings in nsk jni stress tests

[Goetz Lindenmaier]

I backport this for parity with 21.0.9-oracle

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Commit messages:
 - Backport c988d7d6476807bf71a977dc771017915b708ca3

Changes: https://git.openjdk.org/jdk21u-dev/pull/1952/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1952&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8350767
  Stats: 20 lines in 5 files changed: 0 ins; 0 del; 20 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1952.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1952/head:pull/1952

PR: https://git.openjdk.org/jdk21u-dev/pull/1952