RFR: 8338819: JFR: Internal events causes crash when no other events are in use

[Erik Gahlin]

Could I have a review of a PR that fixes an issue with internal events.

Testing: tier1 + jdk/jdk/jfr + manual check

Thanks
Erik

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Commit messages:
 - Initial

Changes: https://git.openjdk.org/jdk/pull/20676/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20676&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8338819
  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/20676.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20676/head:pull/20676

PR: https://git.openjdk.org/jdk/pull/20676