OpenXR API Layers window is not rendered and “NullReferenceException” errors are thrown when the API Layers window is opened

Steps to reproduce:

1. Create a new Unity project using the Universal 3D template
2. Open the Project Settings window (Edit > Project Settings)
3. Open the XR Plugin Management tab in the Project Settings window
4. Click the "Install XR Plugin Management" button
5. Enable OpenXR 
6. Open the OpenXR tab
7. Click the cogwheel button for the API Layers
8. Close the opened API Layers window
9. Repeat step 7
10. Observe the API Layers window and the Console window

Actual results: The API Layers window is not rendered, and "NullReferenceException" errors are thrown

Expected results: The API Layers window renders and no errors are thrown

Reproducible with versions: 1.17.0 (6000.5.0b6, 6000.6.0a4)

Can’t test with versions: 1.16.1 (6000.0.74f1, 6000.3.14f1, 6000.4.5f1) (due to no API Layers function)

Tested on (OS): MacOS Silicon Tahoe 26.3