[clang] [clang] Fix crash caused by undeduced auto return variable (PR #211124)

[Oliver Hunt via cfe-commits]

ojhunt wrote:

So 7b0396f added a containsErrors() gate on the initializer expression, but I'm not sure if that is correct (e.g. as in this case we shouldn't be getting to `getNamedReturnInfo` with a failed initializer), or this error check is too conservative and should simply be checking for any error anywhere?

https://github.com/llvm/llvm-project/pull/211124