Fixes a precedence issue from fe9f55907e
`lib.optionalString <cond> 'text' + 'text2'` will always have 'text2' as
part of the result.
Fixes a precedence issue from fe9f55907e
`lib.optionalString <cond> 'text' + 'text2'` will always have 'text2' as
part of the result.