NullReferenceException in Grid.MeasuredStarredColumns

    Grid.MeasuredStarredColumns (System.Double widthConstraint, System.Double heightConstraint)
    Grid.MeasureAndContractStarredColumns (System.Double width, System.Double height, System.Double totalStarsWidth)
    Grid.MeasureGrid (System.Double width, System.Double height, System.Boolean requestSize)
    Grid.OnSizeRequest (System.Double widthConstraint, System.Double heightConstraint)
    VisualElement.OnMeasure (System.Double widthConstraint, System.Double heightConstraint)
    VisualElement.GetSizeRequest (System.Double widthConstraint, System.Double heightConstraint)
    Layout.GetSizeRequest (System.Double widthConstraint, System.Double heightConstraint)
    VisualElement.Measure (System.Double widthConstraint, System.Double heightConstraint, Xamarin.Forms.MeasureFlags flags)
    FlexLayout+<>c__DisplayClass61_0.<AddChild>b__0 (Xamarin.Flex.Item it, System.Single& w, System.Single& h)
    Item.layout_item (Xamarin.Flex.Item item, System.Single width, System.Single height)
    Item.Layout ()
    FlexLayout.OnMeasure (System.Double widthConstraint, System.Double heightConstraint)
    VisualElement.GetSizeRequest (System.Double widthConstraint, System.Double heightConstraint)
    Layout.GetSizeRequest (System.Double widthConstraint, System.Double heightConstraint)
    VisualElement.Measure (System.Double widthConstraint, System.Double heightConstraint, Xamarin.Forms.MeasureFlags flags)
    StackLayout.CalculateNaiveLayout (Xamarin.Forms.StackLayout+LayoutInformation layout, Xamarin.Forms.StackOrientation orientation, System.Double x, System.Double y, System.Double widthConstraint, System.Double heightConstraint)
    StackLayout.CalculateLayout (Xamarin.Forms.StackLayout+LayoutInformation layout, System.Double x, System.Double y, System.Double widthConstraint, System.Double heightConstraint, System.Boolean processExpanders)
    StackLayout.OnSizeRequest (System.Double widthConstraint, System.Double heightConstraint)
    VisualElement.OnMeasure (System.Double widthConstraint, System.Double heightConstraint)
    VisualElement.GetSizeRequest (System.Double widthConstraint, System.Double heightConstraint)
    Layout.GetSizeRequest (System.Double widthConstraint, System.Double heightConstraint)
    VisualElement.Measure (System.Double widthConstraint, System.Double heightConstraint, Xamarin.Forms.MeasureFlags flags)
    TemplatedView.OnSizeRequest (System.Double widthConstraint, System.Double heightConstraint)
    VisualElement.OnMeasure (System.Double widthConstraint, System.Double heightConstraint)
    VisualElement.GetSizeRequest (System.Double widthConstraint, System.Double heightConstraint)
    Layout.GetSizeRequest (System.Double widthConstraint, System.Double heightConstraint)
    VisualElement.Measure (System.Double widthConstraint, System.Double heightConstraint, Xamarin.Forms.MeasureFlags flags)
    StackLayout.CalculateNaiveLayout (Xamarin.Forms.StackLayout+LayoutInformation layout, Xamarin.Forms.StackOrientation orientation, System.Double x, System.Double y, System.Double widthConstraint, System.Double heightConstraint)
    StackLayout.CalculateLayout (Xamarin.Forms.StackLayout+LayoutInformation layout, System.Double x, System.Double y, System.Double widthConstraint, System.Double heightConstraint, System.Boolean processExpanders)
    StackLayout.OnSizeRequest (System.Double widthConstraint, System.Double heightConstraint)
    VisualElement.OnMeasure (System.Double widthConstraint, System.Double heightConstraint)
    VisualElement.GetSizeRequest (System.Double widthConstraint, System.Double heightConstraint)
    Layout.GetSizeRequest (System.Double widthConstraint, System.Double heightConstraint)
    VisualElement.Measure (System.Double widthConstraint, System.Double heightConstraint, Xamarin.Forms.MeasureFlags flags)
    ScrollView.LayoutChildren (System.Double x, System.Double y, System.Double width, System.Double height)
    Layout.UpdateChildrenLayout ()
    Layout.OnSizeAllocated (System.Double width, System.Double height)
    Layout+<>c.<OnChildMeasureInvalidated>b__45_0 ()
    NSAsyncActionDispatcher.Apply ()
    (wrapper managed-to-native) UIKit.UIApplication.UIApplicationMain(int,string[],intptr,intptr)
    UIApplication.Main (System.String[] args, System.IntPtr principal, System.IntPtr delegate)
    UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName)
    Application.Main (System.String[] args)