[clang] [clang] fix crash substituting decltype parameters during partially ordered deduction (PR #214130)

[Oliver Hunt via cfe-commits]

ojhunt wrote:

Second attempt, trying to do @mizvekov's suggested fix, so if it's correct credit to him, if it's incorrect that's my own muppetry :D

https://github.com/llvm/llvm-project/pull/214130