[beernutz]

I think part of the reason for doing it the way they do in the article is to reduce nesting. I saw the problem with missing the short circuit as well though which is why I like the suggestion of using

  if (isValidUser() && isValidData(data))

And checking for data being null in the isValidData method. There is a little overhead in the call and return if data is null, but the clarity provided seems like a win in these kinds of cases.