"NullReferenceException" and "InvalidOperationException" errors are thrown and Game view doesn't render when entering Play mode after modifying a nested PanelRenderer following in-context UXML editing

Steps to reproduce:

1. Open the attached project
2. Open the "SampleScene"
3. Fully expand the "PanelRenderer" GameObject in the Hierarchy
4. Select the "New UXML.uxml" and click "Open In Context"
5. Duplicate the VisualElement and Save and exit In Context editing
6. Select the "Card" GameObject under "PanelRenderer"
7. In the Inspector, change its "Position" property to "Absolute" or "Relative" (any change triggers the bug)
8. Observe "NullReferenceException" is thrown
9. Enter Play mode
10. Observe the Game view and the Console

Actual results: Multiple "NullReferenceException" errors are spammed with "InvalidOperationException: You can't modify a VisualElement after its resources are released." error and nothing is rendered in the Game view when entering Play mode for the first time

Expected results: No errors and Game view renders all UI elements

Reproducible with versions: 6000.6.0b6, 6000.7.0a4

Can’t test with versions: 6000.3.21f1, 6000.5.6f1 (no in context editing)

Tested on (OS): macOS 26.5, Ubuntu 24.04