[clang] [Clang] Fix a crash when using ast-dump=json (PR #70224)

[via cfe-commits]

elizabethandrews wrote:

I've applied all the review comments. I'm not sure what to do about the failing code format bot though. Should I open a new PR or  can I ignore that bot since I've run clang-format locally?

https://github.com/llvm/llvm-project/pull/70224