I have recently upgraded react-modal from 1.7.1 to 3.1.6. I am now getting a warning in the console whenever react-modal unmounts. ### Steps to reproduce: 1. Mount a component that is using React Modal as a child. 2. Dismount the component has has React Modal as a child. (this happens for me when I navigate between routes) ### Expected behavior: 1. I'm not sure if this warning is due to incorrect implementation on my part or if this is expected behavior. ### Additional notes: The modals are behaving normally, I am just unsure why the focus manager is giving me this warning.