I was trying the animation nodes features, when I tried to render animation it crashed and, for my surprise, the whole node-set is red and "Undefined Socket" labelled.
This is totally a bug that happened while rendering. This is probably not supposed to happen. Try closing blender and restarting your computer. If you are still facing this issue, try recreating the setup. I know it's hard to set it up again, but It is possible. I had to try 7 times just to simulate fire using materials and animating it, but the end result was great.
So don't give up and do what I have said. If it doesn't work, try at least 10 times. If it still doesn't work, I think you are using a version of blender that can't support this kind of stuff. (Which is highly unlikely). And a tip for using this site, don't put stuff or questions regarding the answer as an answer. You can comment on he question instead.