http://www.ootpdevelopments.com/boar...highlight=Null
Some seeds of thought and a place to begin. I learned through my installation that it is probably the best course to fix the very first error you get because future errors are likely built upon its flaws otherwise. So for now, I'd focus on the 0 data somewhere it doesn't belong.
In my case, it took three tries. The first two times I actually deleted everything that Cato had previously produced in order to get as clean a slate as possible. I'm hardly a qualified Cato veteran, but I'd take the advice of those I've heard it from: begin with the first problem and make every attempt to research and solve it. Once that clears, you may encounter a different error message, but handled one at a time the number of occurences will gradually lessen.
All I have for now is the link above, but I'll keep looking for you.