SubScene closes and Reimport hangs indefinitely after a duplicate SubScene's Scene Asset is cleared to None

Steps to reproduce:

1. Create a new 3D URP project
2. Install the Entities package (com.unity.entities)
3. In the Hierarchy, right-click > New Sub Scene and save
4. Duplicate the Sub Scene
5. Select the duplicate scene
6. In the Inspector, uncheck "Auto Load Scene" and in "Scene Asset" property select "None"
7. Delete the duplicate
8. Observe the original scene gets closed
9. Select the original scene and click "Reimport"
10. Observe the "Importing..." text in the Sub Scene Component

Actual results: Setting the duplicate's Scene Asset to None closes the underlying scene, which removes it from under Editor World in the Hierarchy. After deleting the duplicate, clicking Reimport on the remaining SubScene hangs indefinitely on "Importing..." and never completes

Expected results: Clearing a duplicate SubScene's Scene Asset should not close/remove the original scene from Editor World, no exception should be thrown, and Reimport should complete normally

Reproducible with versions: 6000.3.20f1, 6000.5.4f1, 6000.6.0b4, 6000.7.0a2

Can't test with: 6000.0.78f1 (different layout of entities)

Tested on (OS): macoS 26.5

Notes:

• Under some instances, "[Worker0] Exception thrown during SubScene import: System.ArgumentNullException: Cannot add source dependency on empty GUID." is shown after 6-7 steps
• Entering Play mode fixes the issue and restores state