Describe the bug:
When trying to access a site that uses Cloudflare Verification, the "Verifying you are a human" process causes a panic stemming from here https://github.com/servo/servo/blob/main/components/script/layout_dom/element.rs#L746, I believe when it's trying to attach the Cloudflare Turnstile. Unsure if this is because the Shadow DOM implementation is incomplete or something else

To Reproduce:
./mach run https://rateyourmusic.com --pref dom.shadowdom.enabled

Platform:
Windows 10