It wouldn't.
But I think this is such a basic failure mechanism that I don't believe an AI could get to superintelligence without somehow valuing the accuracy and completeness of its model.
Solving this problem - somehow! - is part of the "normal" development of any self-improving AI.
Though note that a reward maximizing AI could still be an existential risk by virtue of turning the entire universe into a busy-beaver counter for its reward. Though this presumes it can't just set reward to float.infinity.
You are the second person to say that the optimization catastrophe includes an assumption that AI arises with a stable value system. That it "somehow" doesn't become a wirehead. Fair enough. I just missed that we were assuming that.
Part 1 was previously posted and it seemed that people likd it, so I figured that I should post part 2 - http://waitbutwhy.com/2015/01/artificial-intelligence-revolution-2.html