“ArgumentNullException: Value cannot be null.” error is thrown when “Add Todo” button is pressed in the APP UI “MVVM And Redux” Sample

Steps to reproduce:

1. Create a new Unity project using the Universal 3D template
2. Open the Package Manager window (Window > Package Management > Package Manager)
3. Install package by name (com.unity.dt.app-ui)
4. Select the App UI package in the Package Manager window
5. Open the Samples tab
6. Import the "MVVM And Redux" sample
7. Open the "Assets/Samples/App UI/2.1.3/MVVM And Redux/Scenes/MVVMRedux.unity" Scene
8. Enter Play Mode
9. Click the "Add Todo" button in the Game View
10. Observe the Console window

Actual results: "ArgumentNullException: Value cannot be null." error is thrown

Expected results: No errors are thrown

Reproducible with versions: 2.1.1, 2.1.3 (6000.0.64f1, 6000.3.3f1, 6000.4.0b2, 6000.5.0a3)

Tested on (OS): MacOS Silicon Tahoe 26.1