Error thrown in xhr.onreadystatechange when javascript execution is suspended/resumed on iOS

The actual approach didn't work. I took the Zepto.js approach (see: https://github.com/madrobby/zepto/pull/633).

In addition to manual and unit tests, I run a angular website with 250k unique visitor a day, I tested this patch there using getsentry.com and got no erros.

See: #5426