Describe the bug

When a control that contains an ItemsRepeater is opened in a new window, the application crashes immediately. This happens even if the ItemsRepeater has no data and no templates applied.

Why is this important?

This issue is serious because it breaks a basic and valid use case. Our application needs to open views in separate windows, and those views often contain an ItemsRepeater. The crash prevents us from using multi window scenarios in any meaningful way. Even the simplest ItemsRepeater with no data causes the window to fail, which blocks core navigation and limits the entire feature set. This affects end users directly since they cannot open or work with content in a new window without the app closing.

Steps to reproduce the bug

1. Create UWP app
2. Add Microsoft.UI.Xaml Nuget package
3. Create a ItemsRepeater in MainPage.xaml
4. Open that MainPage in New Window

Actual behavior

No response

Expected behavior

No response

Screenshots

NuGet package version

WinUI 2 - Microsoft.UI.Xaml 2.8.7

Windows version

Windows 11 (23H2): Build 22631

Additional context

ItemsRepeaterCrash_NewWindow.zip