It's not a typo, it's a deliberate decision to use a hyphen. "no-one" is sometimes used with a hyphen - some people believe that this avoids confusion with the other usage of "no one" meaning "no single", as in
"No one man should have this much power."
So, really it's a matter of preference. "no one" is more formally correct, but since there's a valid argument to use "no-one" when you mean "nobody" and "no one" when you mean "no single" (as detailed above), then I don't think you could say that "no-one" is definitely wrong. Language evolves and changes all the time, depending on people's needs.