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

[Erich Keane via cfe-commits]

erichkeane wrote:

I spent a while debugging this, and this is far from the correct solution.  However, in my debugging I was able to identify the correct solution, so I'll prepare a patch to fix this, closing.

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