[jdk11u-dev] RFR: 8322511: JfrCheckpointThreadClosure::do_thread crashes when fetching thread_id [v2]

[唐佳未]

> Threads which are in the state of `is_attaching_via_jni` may have the NULL object as their `_threadObj` . 
> So the JVM will crash when calling `JfrCheckpointThreadClosure::do_thread()`.

唐佳未 has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  8322511: JfrCheckpointThreadClosure::do_thread crashes when fetching thread_id

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Changes:
  - all: https://git.openjdk.org/jdk11u-dev/pull/2413/files
  - new: https://git.openjdk.org/jdk11u-dev/pull/2413/files/8e7be57f..1244115a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2413&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2413&range=00-01

  Stats: 6 lines in 1 file changed: 0 ins; 4 del; 2 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2413.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2413/head:pull/2413

PR: https://git.openjdk.org/jdk11u-dev/pull/2413