angular/angular.js — pull request #4761 by rthomson83 (2013-11-02 16:38:32+00:00)
Title: fix(httpBackend): IE undefined response in legacy standards mode

Fixes issue #4738. IE10 using IE8 document standards mode has
responseType but response in undefined, responseText has a value in this
scenario.
Solution is to try and fallback to responseText if reponse is empty.