Addresses a case where a `null`-value can sneak in to a reference chain and lead to a live lock. Introduces a regression test which stochastically reproduces the error.
--------- - [x] I confirm that I make this contribution in accordance with the [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai). ------------- Commit messages: - Fixes a livelock in AbstractQueuedSynchronizer Changes: https://git.openjdk.org/jdk/pull/31436/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=31436&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8386085 Stats: 39 lines in 2 files changed: 38 ins; 0 del; 1 mod Patch: https://git.openjdk.org/jdk/pull/31436.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/31436/head:pull/31436 PR: https://git.openjdk.org/jdk/pull/31436
