handle cases in Scene.mount where a falsey value is passed in (f.e. if we pass in `document.body` before it exists, the value is `null`), not just undefined values
handle cases in Scene.mount where a falsey value is passed in (f.e. if we pass in `document.body` before it exists, the value is `null`), not just undefined values

trusktr/infamous,trusktr/infamous,trusktr/infamous