[clang] [clang] [Parse] Avoid mixing enum and non-enum types in ternary expressions. NFC. (PR #159334)

[Martin Storsjö via cfe-commits]

mstorsjo wrote:

Admittedly, this isn't very pretty - the `0` as fallback default in the expressions is more readable indeed, but this looks like the simplest way to avoid warnings here (and this is a somewhat reasonable thing to warn about IMO).

https://github.com/llvm/llvm-project/pull/159334