guard against window globals not being defined, should work better on older browsers and in webworkers

Author: James Halliday

lib/request.js

@@ -203,7 +203,7 @@ var indexOf = function (xs, x) {
 };
 
 var isXHR2Compatible = function (obj) {
-    return obj instanceof window.Blob
-        || obj instanceof window.ArrayBuffer
-        || obj instanceof window.FormData;
+    if (typeof Blob !== 'undefined' && obj instanceof Blob) return true;
+    if (typeof ArrayBuffer !== 'undefined' && obj instanceof ArrayBuffer) return true;
+    if (typeof FormData !== 'undefined' && obj instanceof FormData) return true;
 };