RFR: 8329651: TestLibGraal.java crashes with assert(_stack_base != nullptr)

[David Holmes]

The first thing a new thread does is record its stack size and base. But it is made visible to the rest of the system prior to that. So  we have a risk of trying to print information for a thread that may never have actually executed yet. `Thread::print_on_error` should 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:
 - 8329651: TestLibGraal.java crashes with assert(_stack_base != nullptr)

Changes: https://git.openjdk.org/jdk/pull/18615/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18615&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8329651
  Stats: 5 lines in 1 file changed: 2 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/18615.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18615/head:pull/18615

PR: https://git.openjdk.org/jdk/pull/18615