RFR: 8360045: StringTokenizer.hasMoreTokens() throws NPE after nextToken(null)

[Naoto Sato]

Fixing the side-effect caused by calling `StringTokenizer.nextToken(null)`, where the delimiter is set to `null` even if the method throws an NPE.

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Commit messages:
 - initial commit

Changes: https://git.openjdk.org/jdk/pull/25942/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25942&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8360045
  Stats: 48 lines in 2 files changed: 47 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/25942.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25942/head:pull/25942

PR: https://git.openjdk.org/jdk/pull/25942