Index of Null

I joined a frontline pioneer game 1616393 as Japan. Immediently upon entering I received this error;

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Cannot read property 'indexOf' of null

TypeError: Cannot read property 'indexOf' of null

at hup.ui.UiHelper.preloadImageClassesByNameTag (http://www.callofwar.com/ww2-dev/js/main-built-min.js?bust=1473185550:30424:59)

at hup.ui.TutorialWidget.onInit (http://www.callofwar.com/ww2-dev/js/main-built-min.js?bust=1473185550:85819:21)

at Subscriber.notify (http://www.callofwar.com/ww2-dev/js/main-built-min.js?bust=1473185550:272:7)

at Object.publish (http://www.callofwar.com/ww2-dev/js/main-built-min.js?bust=1473185550:346:33)

at publish (http://www.callofwar.com/ww2-dev/js/main-built-min.js?bust=1473185550:363:28)

at hup.GameStateHandler.tryToInitializeGUIs (http://www.callofwar.com/ww2-dev/js/main-built-min.js?bust=1473185550:47398:29)

at hup.GameStateHandler.onDataLoaded (http://www.callofwar.com/ww2-dev/js/main-built-min.js?bust=1473185550:47371:12)

at Subscriber.notify (http://www.callofwar.com/ww2-dev/js/main-built-min.js?bust=1473185550:272:7)

at Object.publish (http://www.callofwar.com/ww2-dev/js/main-built-min.js?bust=1473185550:346:33)

at hup.model.users.User.onDetailsLoaded (http://www.callofwar.com/ww2-dev/js/main-built-min.js?bust=1473185550:45859:20)

Details:

TypeError: Cannot read property 'indexOf' of null

I did not submit the bug report in game because this error came up immediately. Reloading did not resolve the issue.