[clang] [clang] Bailout when the substitution of template parameter mapping is invalid. (PR #86869)

[Shafik Yaghmour via cfe-commits]

https://github.com/shafik approved this pull request.

LGTM, interesting it looks like we don't do this check in `fromContraintExpr` either.

https://github.com/llvm/llvm-project/pull/86869