UI Builder constantly throws NullReferenceException when dragging objects objects into the window

Steps to reproduce:

1. Open the attached project
2. Select the Main Camera object in the Scene's Hierarchy
3. Drag it over the UI Builder window's Hierarchy or StyleSheets panels
4. Observe the Console window

Actual results: NullReferenceExceptions are thrown when holding the object over the panels

Expected results: No warnings or errors are thrown when dragging objects inside the UI Builder window

Reproducible with versions: 6000.4.0a2, 6000.4.0a3

Not reproducible with versions: 6000.0.59f1, 6000.2.8f1, 6000.3.0b6, 6000.4.0a1

Tested on (OS): macOS 26.0.1

Notes:

• The issue occurs when dragging objects from the Scene's Hierarchy to the UI Builder window 
• The issue does not occur when dragging an object from a Project window

Shortened error message:

• NullReferenceException: Object reference not set to an instance of an object
  Unity.UI.Builder.BuilderExplorerDragger.ExplorerGetDragPreviewFromTarget (UnityEngine.UIElements.VisualElement target, UnityEngine.Vector2 mousePosition){}