Fixed mobile detect

Closes #589

app/js/lib/config.js

@@ -42,7 +42,7 @@ Config.Navigator = {
   retina: window.devicePixelRatio > 1,
   ffos: navigator.userAgent.search(/mobi.+Gecko/i) != -1,
   touch: screen.width <= 768,
-  mobile: screen.width < 480 || navigator.userAgent.search(/iOS|iPhone OS|Android|BlackBerry|BB10|Series ?[64]0|J2ME|MIDP|opera mini|opera mobi|mobi.+Gecko|Windows Phone/i) != -1
+  mobile: screen.width && screen.width < 480 || navigator.userAgent.search(/iOS|iPhone OS|Android|BlackBerry|BB10|Series ?[64]0|J2ME|MIDP|opera mini|opera mobi|mobi.+Gecko|Windows Phone/i) != -1
 };
 
 Config.I18n = {