Although slimes leave no corpse, if you use resurrect a crosshair still comes up where they died. I did not actually try to resurrect though....it was that or a pred ;)
Uh, you are right, currently there is no special handling for slimes. They leave corpses, but there is no graphics for it, so there is just black square. And it can be resurrected.
I know how it should work correctly, I will start working on it soon.