RFR: 8349417: Fix NULL usage from JDK-8346433

[David Holmes]

Trivial replacement of NULL with nullptr

Testing: Windows build

Thanks

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Commit messages:
 - 8349417: Fix NULL usage from JDK-8346433

Changes: https://git.openjdk.org/jdk/pull/23483/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23483&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8349417
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/23483.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23483/head:pull/23483

PR: https://git.openjdk.org/jdk/pull/23483