Removing and readding a set quickly uninentionally hides the set

[noahfinerp]

How to reproduce: Head to an example that involves redrawing the venn diagram (such as this one)[http://benfred.github.io/venn.js/examples/dynamic.html]. Hide and then reshow a circle quickly (before its animation is over)

Here's a gif showing what's going on. If I hide a circle then show it again after it finishes its animation, I get the expected behavior. However, if I toggle the circle quickly, it becomes hidden. The circle comes back after the venn diagram is updated in any other way.