This fallacy argues that because a premise has not be proven false, the premise must be true; or that, because a premise has not be proven true, the premise must be false
Dealt with by pointing out that just becuase something has not yet been proven true does not mean it will not be or visa versa. You simply cannot draw any conclusion. It took 358 years to prove Fermat's Last Theorem. So for all of that period according to this fallacy you would have concluded that the theorem was false because it had not been proven. Yet in the end Andrew Wiles proved the theorem correct.