Well, a food safety expert would tell you that your current plan is a terrible idea. You want to minimize the amount of time food is between 40 F and 140 F, and restaurants have very strict regulations about that. The right way to do it is to put your food in relatively small containers, no more than a quart in size, and put them into the fridge right away. That prevents any possible bacteria growth.
On the other hand, with a slow cooker, your food has been sitting at like 170 or so for many hours, and is likely entirely sterile. The bacteria that live in air are not likely to be harmful to you in any way if you eat them, and they wouldn't grow all that fast on most things that you would have cooked. (This, according to a toxicologist I once knew who would leave baked chicken out on top of the stove overnight!)
The short answer is that if you haven't died yet, you probably won't, but don't tell anyone I told you so! And never do this on anything that hasn't been cooked hot enough to be sterilized!
Personally, I'd just put the food in plastic containers and throw it in the fridge. It's not going to heat up the inside of your fridge enough to hurt anything.