With regards to your original code, shouldn't "and" be instead "&&"?
As for the error message, I'm not sure why it won't accept a zero value. Maybe you could try
if !(_score) then <yourcode>
Oops. Scratch that. The above code actually threw out the same error message that you had (number, expected bool), except my |#| was before "then". The following works, though, at least with my own test (I didn't try your exact code)
if !(_score > 0) then <your code>