I do not believe that to be possible. You can uncheck the option to have the show end with a black slide. What you can do is change the resolution of your screen so that it will fit a slide perfectly, thus negating the need for the black. I changed my resolution to 1400 by 1050 and the slides fit my screen perfectly. To do this, right click anywhere on your desktop screen, go to Properties->Settings and screen resolution is there.

Hope This Helps,
Math Nerd