"GameObject does not reference component Transform. Fixing." error is thrown when creating a Prefab from a UXML object that has nested UXML children in Hierarchy window

Steps to reproduce:
1. Create new Unity project using Universal 3D Template
2. In Hierarchy create Button object (Right-click > UI Toolkit > Standard Elements > Button)
3. In “Open UI stage” pop-up press “Continue” and save UXML file
4. Go back to Hierarchy window from “New UXML” window by pressing “<“ button back
5. Save unsaved UI Stage changes
6. Select “New UXML” object in Hierarchy window
7. Duplicate “New UXML” twice in Hierarchy window
8. Drag two duplicated UXML files inside “New UXML” in Hierarchy window
9. Drag “New UXML” in Project window to create a Prefab
10. Observe the Console window  

Actual results: “[Worker0] GameObject 'New UXML (1)' does not reference component Transform. Fixing.
UnityEngine.UIElements.PanelRenderer:OnPanelRendererCleanup ()” error is thrown in the Console window

Expected results: No errors are thrown in the Console window

Reproducible with versions: 6000.5.4f1, 6000.6.0b5, 6000.7.0a3

Can’t test with versions: 6000.3.20f1 and lower (no Panel Renderer)

Tested on (OS): macOS Tahoe 26.5.2 (M1)

Notes:

•  in 6000.5.4f1 use Panel Renderer Object in Hierarchy window