Spanish is full of contradictions that it's hard to know which is really correct without being a native speaker and having spoken it for long.
Just take negation for example. I know in Spanish negative and affirmative statements are never mixed. But no, there are exceptions to that.
If we follow the convention here:
María no necesita nada.(Maria doesn't need anything (nothing).)
We would think it is correct to say:
Ningunas vacaciones a Alaska no son completas sin una excursión a Mt. Kinley.(no vacation is (not) complete without a trip to Mt.Kinley.)
When in fact it's not correct as it is supposed to be "... son..." instead of "...no son...".