RFR: 8360664: Null pointer dereference in src/hotspot/share/prims/jvmtiTagMap.cpp in IterateOverHeapObjectClosure::do_object() [v2]

[Artem Semenov]

> The defect has been detected and confirmed in the function ```IterateOverHeapObjectClosure::do_object()``` located in the file ```src/hotspot/share/prims/jvmtiTagMap.cpp``` with static code analysis. This defect can potentially lead to a null pointer dereference.
> 
> The pointer ```oop o``` is passed to the constructor of the CallbackWrapper class, where it is dereferenced without a null check.

Artem Semenov 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:

  8360664 Null pointer dereference in src/hotspot/share/prims/jvmtiTagMap.cpp in IterateOverHeapObjectClosure::do_object()
  
  Found by Linux Verification Center (linuxtesting.org) with SVACE.
  signed-off-by: Artem Semenov <savoptik at altlinux.org>

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Changes:
  - all: https://git.openjdk.org/jdk/pull/26002/files
  - new: https://git.openjdk.org/jdk/pull/26002/files/ee6a0ff7..e69c49c8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26002&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26002&range=00-01

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/26002.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26002/head:pull/26002

PR: https://git.openjdk.org/jdk/pull/26002