[Mac Catalyst] NullReferenceException in DragAndDropDelegate - FIX

src/Controls/src/Core/Platform/iOS/DragAndDropDelegate.cs

@@ -122,7 +122,7 @@ session.LocalDragSession.Items[0].LocalObject is CustomLocalStateData cdi &&
 				_viewHandler.VirtualView is View view)
 			{
 				HandleDrop(view, cdi.DataPackage, session, new PlatformDropEventArgs(cdi.View.Handler.PlatformView as UIView, interaction, session));
-				HandleDropCompleted(cdi.View, new PlatformDropCompletedEventArgs(cdi.View.Handler.PlatformView as UIView, interaction, session));
+				HandleDropCompleted(cdi.View, new PlatformDropCompletedEventArgs(cdi.View.Handler?.PlatformView as UIView, interaction, session));
 			}
 			else if (_viewHandler.VirtualView is View v)
 			{

src/Controls/tests/TestCases.HostApp/Issues/Issue28416.xaml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="Maui.Controls.Sample.Issues.Issue28416">
+  <VerticalStackLayout x:Name="stackLayout" AutomationId="StackLayout">
+    <Rectangle x:Name="dragObject" AutomationId="DragObject" Stroke="Red" Fill="DarkBlue" StrokeThickness="4" HeightRequest="200" WidthRequest="200">
+      <Rectangle.GestureRecognizers>
+        <DragGestureRecognizer DropCompleted="DragGestureRecognizer_DropCompleted" />
+      </Rectangle.GestureRecognizers>
+    </Rectangle>
+
+    <Image x:Name="dragTarget" AutomationId="DragTarget" BackgroundColor="Silver" HeightRequest="300" WidthRequest="250">
+      <Image.GestureRecognizers>
+        <DropGestureRecognizer Drop="DropGestureRecognizer_Drop" />
+      </Image.GestureRecognizers>
+    </Image>
+    <Label AutomationId="InstructionsLabel" Text="Drag the blue square onto the silver element" />
+  </VerticalStackLayout>
+</ContentPage>

src/Controls/tests/TestCases.HostApp/Issues/Issue28416.xaml.cs

@@ -0,0 +1,25 @@
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 28416, "Crash in drag-n-drop with dragged element destroyed before drop is completed", PlatformAffected.iOS)]
+public partial class Issue28416 : ContentPage
+{
+	public Issue28416()
+	{
+		InitializeComponent();
+	}
+
+	private void DropGestureRecognizer_Drop(object sender, DropEventArgs e)
+	{
+		stackLayout.Remove(dragObject);
+
+		// This causes the crash.
+		dragObject.Handler = null;
+
+		stackLayout.Add(new Label { AutomationId = "DropResult", Text = "Dropped!" });
+	}
+
+	private void DragGestureRecognizer_DropCompleted(object sender, DropCompletedEventArgs e)
+	{
+		stackLayout.Add(new Label { AutomationId = "DropCompletedResult", Text = "Completed!" });
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue28416.cs

@@ -0,0 +1,28 @@
+#if TEST_FAILS_ON_WINDOWS && TEST_FAILS_ON_ANDROID // "DropCompletedResult" does not appear on Windows. Issues: https://github.com/dotnet/maui/issues/28448 and https://github.com/dotnet/maui/issues/17554
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+[Category(UITestCategories.DragAndDrop)]
+public class Issue28416 : _IssuesUITest
+{
+	public Issue28416(TestDevice testDevice) : base(testDevice)
+	{
+	}
+
+	protected override bool ResetAfterEachTest => true;
+
+	public override string Issue => "Crash in drag-n-drop with dragged element destroyed before drop is completed";
+
+	[Test]
+	public void DragAndDropWithAnElementThatIsRemoved()
+	{
+		App.WaitForElement("InstructionsLabel");
+		App.DragAndDrop("DragObject", "DragTarget");
+		App.WaitForElement("DropResult");
+		App.WaitForElement("DropCompletedResult");
+	}
+}
+#endif