[clang] [Clang][Sema] Fix crash when MS dependent base class lookup occurs in an incomplete context (PR #83024)

[Krystian Stasiowski via cfe-commits]

sdkrystian wrote:

> Side note: In the future can you be more descriptive with follow up commit messages, isntead of just `[FOLD]`. That doesn't really tell me whether I need to re-review/give context, particularly since I do much of that triage in email.

Apologies -- I'll keep this in mind for future contributions :) 



https://github.com/llvm/llvm-project/pull/83024