NullReferenceException is thrown when quickly deleting UI elements one-by-one in scene context

Steps to reproduce:

1. Create and open a new project
2. Open 'Edit -> Project Settings -> UI Toolkit'
3. Enable 'in-scene UI Authoring'
4. In Hierarchy, right-click -> UI Toolkit -> Standard Elements -> Visual Element
5. Duplicate the VisualElement 10 times
6. Select the first VisualElement
7. Delete it
8. Repeat steps 6-7 in a quick succession
9. Observe the Console

Actual results: "NullReferenceException: Object reference not set to an instance of an object
Unity.UIToolkit.Editor.UxmlAssetUtilities.SynchronizePath" is thrown

Expected results: No errors are thrown

Reproducible with versions: 6000.7.0a6

Not reproducible with versions: 6000.6.0b1, 6000.6.1f1, 6000.7.0a5

Can’t test with versions: 6000.0.83f1, 6000.3.24f1 (No UI Authoring in Scene)

Tested on (OS): Windows 11 Pro (25H2)

Notes:

• Reproducible both in main stage and UI stage