Add Support for Popups inside a Modal NavigationPage

src/CommunityToolkit.Maui.UnitTests/Views/Popup/PopupPageTests.cs

@@ -296,6 +296,35 @@ void HandlePopupPageClosed(object? sender, IPopupResult e)
 		}
 	}
 
+	[Fact]
+	public async Task ShowPopupAsync_FromModalNavigationPage_ShouldCloseSuccessfully()
+	{
+		// Remove shell navigation
+		Application.Current?.Windows[0].Page = new ContentPage() { Title = "Root" };
+		var rootPage = Application.Current?.Windows[0].Page as ContentPage ?? throw new InvalidOperationException("Root page must be a ContentPage");
+
+		var modalNavigationPage = new NavigationPage(new ContentPage() { Title = "Modal Navigation Page" });
+		var popup = new Popup<string>();
+
+		// Act - Push modal navigation page
+		await rootPage.Navigation.PushModalAsync(modalNavigationPage, false);
+
+		// Assert - Verify modal stack has the modal navigation page
+		Assert.Single(rootPage.Navigation.ModalStack);
+		Assert.Same(modalNavigationPage, rootPage.Navigation.ModalStack[0]);
+
+		// Act
+		var showPopupAsyncTask = modalNavigationPage.ShowPopupAsync<string>(popup, token: TestContext.Current.CancellationToken);
+		await popup.CloseAsync("Hello", TestContext.Current.CancellationToken);
+		var result = await showPopupAsyncTask;
+
+		// Assert
+		result.Result.Should().Be("Hello");
+
+		// Cleanup
+		await rootPage.Navigation.PopModalAsync(false);
+	}
+
 	[Fact]
 	public void PopupPageT_Close_ShouldThrowOperationCanceledException_WhenTokenIsCancelled()
 	{

src/CommunityToolkit.Maui/Views/Popup/Popup.shared.cs

@@ -125,4 +125,4 @@ public sealed class PopupBlockedException(in Page currentVisibleModalPage) : Inv
 /// <summary>
 /// An <see cref="InvalidOperationException"/> thrown when an invalid operation is performed on a <see cref="Popup"/>.
 /// </summary>
-public class InvalidPopupOperationException(in string message) : InvalidOperationException(message);
+public class InvalidPopupOperationException(in string message) : InvalidOperationException(message);

src/CommunityToolkit.Maui/Views/Popup/PopupPage.shared.cs

@@ -80,7 +80,7 @@ public async Task CloseAsync(PopupResult result, CancellationToken token = defau
 		var customPageContainer = Navigation.ModalStack.OfType<IPageContainer<Page>>().LastOrDefault();
 		if (customPageContainer is not null && customPageContainer.CurrentPage is not PopupPage)
 		{
-			throw new PopupNotFoundException();
+			customPageContainer = null;
 		}
 
 		var popupPageToClose = customPageContainer?.CurrentPage as PopupPage