It was just a texture loading thing. The next instant after I took that shot she had her top back. Usually the torsos are just invisible - looks like the different tops are the entire torso, just like most games. However, for certain Klingon female tops (the more Duras-sisters type), looks like there's a piece that goes over a doll-torso. Interesting; you'd think it'd just be all one piece like the others.
Screen-shot, because screenshot thread: