[jdk25u] RFR: 8371740 : LinkedTransferQueue.poll() returns null even though queue is not empty

[Viktor Klang]

This fixes a situation where LinkedTransferQueue.poll() may return `null` when the queue is provably non-empty.

This PR is a backport of https://bugs.openjdk.org/browse/JDK-8371740 commit [d350158e](https://github.com/openjdk/jdk/commit/d350158e060c01acf49759dcbdd1f4d72530111b) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository.

The commit being backported was authored by Viktor Klang on 27 Nov 2025 and was reviewed by Alan Bateman.

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Commit messages:
 - Backport d350158e060c01acf49759dcbdd1f4d72530111b

Changes: https://git.openjdk.org/jdk25u/pull/396/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk25u&pr=396&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8371740
  Stats: 87 lines in 2 files changed: 80 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk25u/pull/396.diff
  Fetch: git fetch https://git.openjdk.org/jdk25u.git pull/396/head:pull/396

PR: https://git.openjdk.org/jdk25u/pull/396