An unhandled exception occured

Hello,

After update Xamarin.Forms to 1.4.4.6392 when I use an ActivityIndicator my application fall with "An unhandled exception occured".

The code is simple:

ActivityIndicator activityIndicator = new ActivityIndicator
{
Color = Device.OnPlatform(Color.Black, Color.Default, Color.Default),
IsRunning = true,
VerticalOptions = LayoutOptions.CenterAndExpand
};

  this.Content = new StackLayout
  {
    Children = 
            {
                header,
                activityIndicator
            }
  };