ded/reqwest — pull request #94 by gabalafou (2012-12-20 19:07:56+00:00)
Title: Make readystatechange handler a no-op on readyState 4

Setting onreadystatechange to undefined causes an error to pop up
in IE8:
http://jsbin.com/ulitew/1/edit

Setting it to null also seems to create problems in earlier IE's:
https://issues.jboss.org/browse/JBSEAM-1271

Since setting it to a no-op is what jQuery does, I assume that this
is probably the most browser-compatible technique.