In the razor file called _Root.Head.cshtml there is an if statement that checks to see if the UserAgent contains the text "Android 2.3"
if (Request.UserAgent.IndexOf("Android 2.3", StringComparison.InvariantCultureIgnoreCase) > 0)
{
isAndroid23Class = "android23";
}
However, the UserAgent could be null and an exception will be thrown. The code should be written like this
if (Request.UserAgent != null &&
Request.UserAgent.IndexOf("Android 2.3", StringComparison.InvariantCultureIgnoreCase) > 0)
{
isAndroid23Class = "android23";
}