XHR interceptor minor bug fix

A minor bug prevented the $isArrayProto property from being correctly
read when parsing responses.

Change-Id: I6ab9b1fc1b03eccc96d0a940d72f34399b5823f5
diff --git a/src/injections/xhrInterceptor.js b/src/injections/xhrInterceptor.js
index 6dba13e..07742dd 100644
--- a/src/injections/xhrInterceptor.js
+++ b/src/injections/xhrInterceptor.js
@@ -82,7 +82,7 @@
                 utils.matchInterceptors('response', this.$TWPTRequestURL);
             if (interceptors.length > 0) {
               this.xhr.addEventListener('load', function() {
-                var body = utils.getResponseJSON(this);
+                var body = utils.getResponseJSON(proxyThis);
                 if (body !== undefined)
                   interceptors.forEach(i => {
                     utils.triggerEvent(i.eventName, body, proxyThis.$TWPTID);