Trying to maintain with a straight face that a married couple lives in two different states would be .... difficult.
The idea that a president and his or her running mate must be from the same state is false.
Even if it was not, I'm sure most people wouldn't care. Most of the candidates in 2012 were actually resident in Virginia or DC, yet no one ever bothered mentioning that. One could easily register in DC and the other in the home state. But again, there's no need as no requirement exists.