DOM nodes added by extensions cause failure

Hi, it looks like there are cases where DOM nodes being added by extensions cause the polyfill to choke. I'm my specific case it's using Windows 11, Firefox, Grammarly desktop, and a website built using a common pattern of hiding the body element until the polyfill has finished executing. I imagine this should probably be handled since website visitors would have no understanding as to why they just see an empty page. I can take a look at doing a PR if that's the direction the maintainers want to take.