fix WindowsHandler

public/main/js/app.js

@@ -1014,7 +1014,7 @@ function initializeRewards() {
     });
 
     // Close model - Back button on phone
-    WindowEventHandlers.onpopstate = function (event) {
+    window.onpopstate = function (event) {
         if (!rewardModal.classList.contains('hidden')) {
             event.preventDefault();
             event.stopPropagation();