I agree with aphyr's response to you. This has never been a problem for me. I think your issue is that you consider an empty string to be a sensible default representing false or nil.
I fully agree that those sane defaults indeed aren't right for representing false or nil. What I'm arguing is rather the reverse: nil is often initially used as an (insane?) default and that is later changed without updating all related checks (because they don't stick out and demand attention, which makes them easy to overlook or 'overthink'), which causes bugs.