Steps to reproduce:
1. Open the attached “IN-152886_UIToolkitDebugger.zip” project
2. Open SampleScene
3. Enter PlayMode
4. Open Window > UI Toolkit > Debugger
5. Select Panel: New Panel Settings
6. Pick Element and select the button
7. Exit PlayMode
8. Observe the Game View and Console windows
Actual results: Button disappears from Game View and a InvalidOperationException, followed by a continuous stream of NullReferenceExceptions are thrown in the Console
Expected results: Button is visible and no errors are thrown
Reproducible with: 6000.6.1f1, 6000.7.0a1, 6000.7.0a6
Not reproducible with: 6000.6.0a7
Could not test with: 6000.0.83f1, 6000.3.24f1 (No PanelRenderer Component)
Reproducible on: macOS Sequoia 15.7.9 (M1 Max)
Not reproducible on: No other environments tested