Function.prototype.apply can be undefined

Hi,

our js error tracker is telling us that `Function.prototype.apply` in this line
https://github.com/Gozala/events/blob/f6f6a376252519dfc27740b5b7fb7d69fcde44f1/events.js#L28 can be undefined and then calling `call` on it raises an error. It mainly happens on ios with safari but also sometimes on chrome (ios).
Do you have any idea why this can happens and how to fix it?

Thanks!