RFR: 8329864: TestLibGraal.java still crashes with assert(_stack_base != nullptr)

[David Holmes]

The changes to `JavaThread::print_on_error` were overlooked when `Thread::print_on_error` was fixed by https://github.com/openjdk/jdk/pull/18615. The fix is identical: access the `_stack_base` and `_stack_size` fields directly, not through the accessors with the assert.

Testing:
- tiers 1-3 sanity

Thanks

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Commit messages:
 - 8329864: TestLibGraal.java still crashes with assert(_stack_base != nullptr)

Changes: https://git.openjdk.org/jdk/pull/18683/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18683&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8329864
  Stats: 4 lines in 1 file changed: 2 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/18683.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18683/head:pull/18683

PR: https://git.openjdk.org/jdk/pull/18683