Predator and CL could not provide any possible suspects.
Using Code Search for the file, "position.cpp" and "Node.cpp" assigning to the concern owner who might be related.

@yosin -- Could you please look into the issue, kindly re-assign if this is not related to your changes.
Thank You.

yoihico@, PTAL, it is caused by LayoutSelection::Commit()

ClusterFuzz has detected this issue as fixed in range 499699:499749.

Detailed report: https://clusterfuzz.com/testcase?key=6186961856626688

Fuzzer: bj_broddelwerk
Job Type: windows_syzyasan_chrome
Platform Id: windows

Crash Type: Null-dereference
Crash Address: 0x0000000b
Crash State:
  blink::Node::UpdateDistribution
  blink::ComparePositions
  blink::PositionTemplate<blink::EditingAlgorithm<blink::FlatTreeTraversal> >::ope
  
Memory Tool: SYZYASAN

Regressed: https://clusterfuzz.com/revisions?job=windows_syzyasan_chrome&range=498677:498753
Fixed: https://clusterfuzz.com/revisions?job=windows_syzyasan_chrome&range=499699:499749

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=6186961856626688

Additional requirements: Requires Gestures

See https://github.com/google/clusterfuzz-tools for more information.

If you suspect that the result above is incorrect, try re-doing that job on the test case report page.