1207 UniformItemsLayout NoItems crash (#1220)

samples/CommunityToolkit.Maui.Sample/Pages/Layouts/UniformItemsLayoutPage.xaml

@@ -114,6 +114,15 @@
                     </StackLayout>
                 </StackLayout>
             </mct:UniformItemsLayout>
+
+            <Button Text="Add Random item" Command="{Binding AddItemCommand}" HorizontalOptions="Center" VerticalOptions="Center" Padding="8"/>
+            <mct:UniformItemsLayout BindableLayout.ItemsSource="{Binding Items}">
+                <BindableLayout.ItemTemplate>
+                    <DataTemplate>
+                        <Label Text="{Binding}" />
+                    </DataTemplate>
+                </BindableLayout.ItemTemplate>
+            </mct:UniformItemsLayout>
         </VerticalStackLayout>
     </ScrollView>
 </pages:BasePage>

samples/CommunityToolkit.Maui.Sample/ViewModels/Layouts/UniformItemsLayoutViewModel.cs

@@ -1,6 +1,16 @@
-namespace CommunityToolkit.Maui.Sample.ViewModels.Layouts;
+using System.Collections.ObjectModel;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
 
-public class UniformItemsLayoutViewModel : BaseViewModel
+namespace CommunityToolkit.Maui.Sample.ViewModels.Layouts;
+
+public partial class UniformItemsLayoutViewModel : BaseViewModel
 {
+	[RelayCommand]
+	void AddItem()
+	{
+		Items.Add(Path.GetRandomFileName());
+	}
 
+	public ObservableCollection<string> Items { get; } = new();
 }

src/CommunityToolkit.Maui.Core/Layouts/UniformItemsLayoutManager.shared.cs

@@ -65,7 +65,7 @@ public override Size Measure(double widthConstraint, double heightConstraint)
 
 		if (childWidth == 0)
 		{
-			var sizeRequest = visibleChildren[0].Measure(double.PositiveInfinity, double.PositiveInfinity);
+			var sizeRequest = visibleChildren.Length == 0 ? Size.Zero : visibleChildren[0].Measure(double.PositiveInfinity, double.PositiveInfinity);
 
 			childWidth = sizeRequest.Width;
 			childHeight = sizeRequest.Height;

src/CommunityToolkit.Maui.UnitTests/Layouts/UniformItemsLayoutTests.cs

@@ -59,6 +59,17 @@ public void MeasureUniformItemsLayout_NoWrap()
 		Assert.Equal(expectedSize, actualSize);
 	}
 
+	[Fact]
+	public void MeasureUniformItemsLayout_NoItems_ZeroSize()
+	{
+		var expectedSize = Size.Zero;
+		var emptyUniformItemsLayout = new UniformItemsLayout();
+
+		var actualSize = emptyUniformItemsLayout.CrossPlatformMeasure(double.PositiveInfinity, double.PositiveInfinity);
+
+		Assert.Equal(expectedSize, actualSize);
+	}
+
 	[Fact]
 	public void MeasureUniformItemsLayout_WrapOnNextRow()
 	{