This method will slightly change the existing behavior of webfontloader. Currently, the `insertInto` method grabs the documentElement if the target element doesn't exist yet, instead of failing: https://github.com/typekit/webfontloader/blob/1ea638d4612a2a79fd06072399154de25ecdfae9/src/core/domhelper.js#L64

I'm not sure what effect this will have on different badly formed pages, but it seems safest to keep the exact same behavior as we currently have in this case, no?