If Ross has 2 windows separated by a mullion then it's likely the stud pocket behind the mullion does have a stud. But, that stud will be under a continuous header the goes over both windows. It's load bearing, technically. I don't get too worried about these unless there are 3 windows and they are like 4 feet wide or a center wide fixed window with two flankers.
@Ross, if you put in a shallow box and don't cut more than say half the stud depth, you should be OK. However, it won't pass inspection because of another part of the Building Code. You will be in violation of the hole set back or centering covered under framing:
The diameter of drilled holes in studs should not exceed 40 percent of the stud depth, and the minimum edge distance to the boundary of the hole shall not be less than 5/8-inch. When studs are doubled, drilled holes should not exceed 60 percent of the stud depth. Holes of maximum diameter should not occur in more than two consecutive studs. Adjacent holes, or holes and notches should not occur in the same cross section. As an example, a 2x4 can have a maximum hole of 1 3/8-inch or 2 inches if studs are doubled.
Is there no splash under these windows? I would think if installing the required outlet 24" from the sink could be overruled by the fact that there is no practical way to do this w/o violating the code. Sometimes you can add a receptacle in the cabinet but most of the time the only available area is at a cabinet end. How about some pics?