"InvalidCastException: Specified cast is not valid." is thrown when clicking the deprecation warning box in the "Built-in (Deprecated)" shader dropdown

Steps to reproduce:

1. Create a new project using Universal 3D template
2. In the Project window, right-click > Create > Material
3. Select the newly created Material
4. In the Inspector, click on the dropdown next to "Shader"
5. Click on the "Built-in (Deprecated)" option
6. Click on the warning box ("A Scriptable Render Pipeline is active. Built-in shaders are deprecated.")
7. Observe the Console

Actual results: "InvalidCastException: Specified cast is not valid." error is thrown with each click

Expected results: No errors

Reproducible with versions: 6000.5.0b12, 6000.6.0a7

Can’t test with versions: 6000.4.10f1 (no deprecation box)

Tested on (OS): Windows 11, macOS 26.5