How to fix 'NaN is not a valid value for height'

I'm trying to create a Grid Layout. I can't find any "Template" option for when binding to a ViewModel, so I'm trying to hand roll this thing.

Here's my XML

<ScrollView x:Name="ModuleScrolLView"
            BackgroundColor="#d3d6db">
    <StackLayout x:Name="ModuleStackLayout" 
                 Orientation="Vertical" 
                 VerticalOptions="FillAndExpand">
        <Grid x:Name="SegmentGrid"
              RowSpacing="10"
              ColumnSpacing="10"
              VerticalOptions="StartAndExpand">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*" />
                <ColumnDefinition Width="*" />
            </Grid.ColumnDefinitions>
        </Grid>
        <WebView Source="{Binding DescriptionHtml}" BackgroundColor="White" />
    </StackLayout>
</ScrollView>

And here's my code behind

public partial class Module : ContentPage
{
    private readonly ModulePageViewModel _viewModel;

    public Module()
    {
        _viewModel = new ModulePageViewModel();

        InitializeComponent();
        BindingContext = _viewModel;

        var subscriber = new ModuleSubscription();
        WatchForViewModelUpdates(subscriber);
    }

    private void WatchForViewModelUpdates(ModuleSubscription subscriber)
    {
        MessagingCenter.Subscribe<MainMenu, ModulePageViewModel>(subscriber, "CurrentModuleMessage", (s, e) =>
        {
            subscriber.CurrentModule = e;
            _viewModel.Title = e.Title;
            _viewModel.Description = e.Description;
            _viewModel.Segments = FetchSegmentListAsync(e.Id).Result;
            BuildSegmentCards();
        });
    }

    private static Task<IList<SegmentViewModel>> FetchSegmentListAsync(Guid id)
    {
        var segmentService = App.Container.Resolve<ISegmentService>();
        return Task.Run(() => segmentService.FindByModuleId(id));
    }


    private void BuildSegmentCards()
    {
        var grid = ((Grid)SegmentGrid);
        grid.RowDefinitions.Clear();

        for (var i = 0; i < _viewModel.Segments.Count; i++)
        {
            var column = i % 2;
            var row = i / 2; // ints round up (1.5 rounds to 2)
            if (row % 2 != 0)
            {
                grid.RowDefinitions.Add(new RowDefinition { Height = new GridLength(1, GridUnitType.Star) });
            }

            grid.Children.Add(BuildFrame(_viewModel.Segments[i]), column, row);
        }
    }

    private Frame BuildFrame(SegmentViewModel value)
    {
        var palleteFrame = new Frame
        {
            BackgroundColor = Color.White,
            Padding = 12,
            Content = CreateStack(value),
            HasShadow = false,
            VerticalOptions = LayoutOptions.FillAndExpand
        };

        return palleteFrame;
    }

    private StackLayout CreateStack(SegmentViewModel value)
    {
        var stack = new StackLayout
        {
            Spacing = 3,
            Orientation = StackOrientation.Vertical,
            VerticalOptions = LayoutOptions.FillAndExpand,
            Children =
            {
                new Label {Text = value.Number.ToString(), BackgroundColor = Color.White, TextColor = Color.Aqua.WithLuminosity(0.3f)},
                new Label {Text = value.Title, BackgroundColor = Color.White, TextColor = Color.Aqua.WithLuminosity(0.3f)},
            },
        };

        return stack;
    }

The problem I'm getting is the error

NaN is not a valid value for height

How can I fix this?

06-16 14:32:55.651 E/SQLiteLog( 4732): (1) statement aborts at 2: [ROLLBACK] cannot rollback - no transaction is active
06-16 14:32:55.651 E/mono    ( 4732): 
06-16 14:32:55.651 E/mono    ( 4732): Unhandled Exception:
06-16 14:32:55.651 E/mono    ( 4732): System.ArgumentException: NaN is not a valid value for height
06-16 14:32:55.651 E/mono    ( 4732):   at Xamarin.Forms.Size..ctor (Double width, Double height) [0x00000] in <filename unknown>:0 
06-16 14:32:55.651 E/mono    ( 4732):   at Xamarin.Forms.StackLayout.SumOfSizeRequests (Double widthConstraint, Double heightConstraint, System.Int32& numOfExpanders) [0x00000] in <filename unknown>:0 
06-16 14:32:55.651 E/mono    ( 4732):   at Xamarin.Forms.StackLayout.OnSizeRequest (Double widthConstraint, Double heightConstraint) [0x00000] in <filename unknown>:0 
06-16 14:32:55.651 E/mono    ( 4732):   at Xamarin.Forms.VisualElement.GetSizeRequest (Double widthConstraint, Double heightConstraint) [0x00000] in <filename unknown>:0 
06-16 14:32:55.651 E/mono    ( 4732):   at Xamarin.Forms.Layout.GetSizeRequest (Double widthConstraint, Double heightConstraint) [0x00000] in <filename unknown>:0 
06-16 14:32:55.651 E/mono    ( 4732):   at Xamarin.Forms.ScrollView.LayoutChildren (Double x, Double y, Double width, Double height) [0x00000] in <filename unknown>:0 
06-16 14:32:55.651 E/mono    ( 4732):   at Xamarin.Forms.Layout.UpdateChildrenLayout () [0x00000] in <filename unknown>:0 
06-16 14:32:55.651 E/mono    ( 4732):   at Xamarin.Forms.Layout.OnSizeAllocated (Double width, Double height) [0x0
06-16 14:32:55.651 E/mono-rt ( 4732): [ERROR] FATAL UNHANDLED EXCEPTION: System.ArgumentException: NaN is not a valid value for height
06-16 14:32:55.651 E/mono-rt ( 4732):   at Xamarin.Forms.Size..ctor (Double width, Double height) [0x00000] in <filename unknown>:0 
06-16 14:32:55.651 E/mono-rt ( 4732):   at Xamarin.Forms.StackLayout.SumOfSizeRequests (Double widthConstraint, Double heightConstraint, System.Int32& numOfExpanders) [0x00000] in <filename unknown>:0 
06-16 14:32:55.651 E/mono-rt ( 4732):   at Xamarin.Forms.StackLayout.OnSizeRequest (Double widthConstraint, Double heightConstraint) [0x00000] in <filename unknown>:0 
06-16 14:32:55.651 E/mono-rt ( 4732):   at Xamarin.Forms.VisualElement.GetSizeRequest (Double widthConstraint, Double heightConstraint) [0x00000] in <filename unknown>:0 
06-16 14:32:55.651 E/mono-rt ( 4732):   at Xamarin.Forms.Layout.GetSizeRequest (Double widthConstraint, Double heightConstraint) [0x00000] in <filename unknown>:0 
06-16 14:32:55.651 E/mono-rt ( 4732):   at Xamarin.Forms.ScrollView.LayoutChildren (Double x, Double y, Double width, Double height) [0x00000] in <filename unknown>:0 
06-16 14:32:55.651 E/mono-rt ( 4732):   at Xamarin.Forms.Layout.UpdateChildrenLayout () [0x00000] in <filename unknown>:0 
06-16 14:32:55.651 E/mono-rt ( 4732):   at Xamarin.Forms.Layout.OnSizeAllocated (Double width, Double