validate(0) return false

[xmtoken]

numbro.validate(0, {});
result: false
expected: true

https://github.com/BenjaminVanRyseghem/numbro/blob/2.2.0/src/validating.js#L251
I think unformatter.unformat will return undefined if unformat fails.
So I think I should fix the above code to return value !== undefined;, but I want more help with this library in detail