Bad Monkey: NullReferenceException

[OzBob]

running the latest master branch code and testing 'monkey' gives the following error:

λ dotnet run --project samples/Samples.csproj
PRESENT http://localhost:8080/sample-picker
Listening at http://*:8080/...
GET /sample-picker
GET /ooui.js
WEBSOCKET /sample-picker
GET /monkeys
GET /ooui.js
Failed to create element: System.NullReferenceException: Object reference not set to an instance of an object.
at Xamarin.Forms.Grid.AssignAbsoluteCells() in D:\a\1\s\Xamarin.Forms.Core\GridCalc.cs:line 92
at Xamarin.Forms.Grid.MeasureGrid(Double width, Double height, Boolean requestSize) in D:\a\1\s\Xamarin.Forms.Core\GridCalc.cs:line 483
at Xamarin.Forms.Grid.OnSizeRequest(Double widthConstraint, Double heightConstraint) in D:\a\1\s\Xamarin.Forms.Core\GridCalc.cs:line 60
at Xamarin.Forms.VisualElement.OnMeasure(Double widthConstraint, Double heightConstraint) in D:\a\1\s\Xamarin.Forms.Core\VisualElement.cs:line 776
at Xamarin.Forms.VisualElement.GetSizeRequest(Double widthConstraint, Double heightConstraint) in D:\a\1\s\Xamarin.Forms.Core\VisualElement.cs:line 658
at Xamarin.Forms.Layout.GetSizeRequest(Double widthConstraint, Double heightConstraint) in D:\a\1\s\Xamarin.Forms.Core\Layout.cs:line 132
at Xamarin.Forms.VisualElement.Measure(Double widthConstraint, Double heightConstraint, MeasureFlags flags) in D:\a\1\s\Xamarin.Forms.Core\VisualElement.cs:line 705
at Ooui.Forms.Renderers.ListViewRenderer.CalculateHeightForCell(Cell cell) in D:\a\Repos\praeclarum\Ooui\Ooui.Forms\Renderers\ListViewRenderer.cs:line 284
at Ooui.Forms.Renderers.ListViewRenderer.UpdateItems() in D:\a\Repos\praeclarum\Ooui\Ooui.Forms\Renderers\ListViewRenderer.cs:line 191
at Ooui.Forms.Renderers.ListViewRenderer.OnElementChanged(ElementChangedEventArgs1 e) in D:\a\Repos\praeclarum\Ooui\Ooui.Forms\Renderers\ListViewRenderer.cs:line 61 at Ooui.Forms.VisualElementRenderer1.SetElement(TElement element) in D:\a\Repos\praeclarum\Ooui\Ooui.Forms\VisualElementRenderer.cs:line 121
at Ooui.Forms.VisualElementRenderer1.Ooui.Forms.IVisualElementRenderer.SetElement(VisualElement element) in D:\a\Repos\praeclarum\Ooui\Ooui.Forms\VisualElementRenderer.cs:line 87 at Ooui.Forms.Platform.CreateRenderer(VisualElement element) in D:\a\Repos\praeclarum\Ooui\Ooui.Forms\Platform.cs:line 84 at Ooui.Forms.VisualElementPackager.OnChildAdded(VisualElement view) in D:\a\Repos\praeclarum\Ooui\Ooui.Forms\VisualElementPackager.cs:line 71 at Ooui.Forms.VisualElementPackager.Load() in D:\a\Repos\praeclarum\Ooui\Ooui.Forms\VisualElementPackager.cs:line 40 at Ooui.Forms.VisualElementRenderer1.SetElement(TElement element) in D:\a\Repos\praeclarum\Ooui\Ooui.Forms\VisualElementRenderer.cs:line 109
at Ooui.Forms.VisualElementRenderer1.Ooui.Forms.IVisualElementRenderer.SetElement(VisualElement element) in D:\a\Repos\praeclarum\Ooui\Ooui.Forms\VisualElementRenderer.cs:line 87 at Ooui.Forms.Platform.CreateRenderer(VisualElement element) in D:\a\Repos\praeclarum\Ooui\Ooui.Forms\Platform.cs:line 84 at Ooui.Forms.VisualElementPackager.OnChildAdded(VisualElement view) in D:\a\Repos\praeclarum\Ooui\Ooui.Forms\VisualElementPackager.cs:line 71 at Ooui.Forms.VisualElementPackager.Load() in D:\a\Repos\praeclarum\Ooui\Ooui.Forms\VisualElementPackager.cs:line 40 at Ooui.Forms.VisualElementRenderer1.SetElement(TElement element) in D:\a\Repos\praeclarum\Ooui\Ooui.Forms\VisualElementRenderer.cs:line 109
at Ooui.Forms.VisualElementRenderer1.Ooui.Forms.IVisualElementRenderer.SetElement(VisualElement element) in D:\a\Repos\praeclarum\Ooui\Ooui.Forms\VisualElementRenderer.cs:line 87 at Ooui.Forms.Platform.CreateRenderer(VisualElement element) in D:\a\Repos\praeclarum\Ooui\Ooui.Forms\Platform.cs:line 84 at Ooui.Forms.Platform.AddChild(VisualElement view) in D:\a\Repos\praeclarum\Ooui\Ooui.Forms\Platform.cs:line 167 at Ooui.Forms.Platform.SetPage(Page newRoot) in D:\a\Repos\praeclarum\Ooui\Ooui.Forms\Platform.cs:line 127 at Xamarin.Forms.PageExtensions.CreateElement(Page page) in D:\a\Repos\praeclarum\Ooui\Ooui.Forms\PageExtensions.cs:line 40 at Xamarin.Forms.PageExtensions.GetOouiElement(Page page) in D:\a\Repos\praeclarum\Ooui\Ooui.Forms\PageExtensions.cs:line 30 at Samples.MonkeysSample.CreateElement() in D:\a\Repos\praeclarum\Ooui\samples\MonkeysSample.cs:line 17 at System.Lazy1.ViaFactory(LazyThreadSafetyMode mode)
at System.Lazy1.ExecutionAndPublication(LazyHelper executionAndPublication, Boolean useDefaultConstructor) at System.Lazy1.CreateValue()
at Ooui.UI.ElementHandler.GetElement() in D:\a\Repos\praeclarum\Ooui\Ooui\UI.cs:line 345
at Ooui.UI.d__65.MoveNext() in D:\a\Repos\praeclarum\Ooui\Ooui\UI.cs:line 521