Fix DecodeError.MissingKeyPath handling thrown from decode()
Fix DecodeError.MissingKeyPath handling thrown from decode()

If you throw `DecodeError.MissingKeyPath` from `static func decode(e: Extractor) throws -> DecodedType`, the error was not correctly ignored in `Extractor.valueOptional()` or the `<|?` operator.

ikesyo/Himotoki,ikesyo/Himotoki