Don't fail element.animate() on iOS because of style patch fail

Quick fix for https://github.com/web-animations/web-animations-js/issues/8. We should do something better than dying if the inline style patch fails.
Repro'd and fixed on iOS Safari "Mozilla/5.0 (iPhone; CPU iPhone OS 7_1 like Mac OS X) AppleWebKit/537.51.2 (KHTML, like Gecko) Version/7.0 Mobile/11D167 Safari/9537.53".

Not sure about iOS 8.