[clang] [Clang][Sema] Fix NULL dereferences for invalid references (PR #77703)

[Shafik Yaghmour via cfe-commits]

https://github.com/shafik requested changes to this pull request.

I don't believe this is the right approach. 

I can only replicate one of the issues: https://godbolt.org/z/7dee3a3cY

I spent some time looking at it and it is quite gnarly but we need to understand better what is going on. 

https://github.com/llvm/llvm-project/pull/77703