GTK GameObject Node loses its Scene reference when the Scene is unloaded

How to reproduce:

1. Open the attached "IN-147058_GTK Test Issues.zip" project
2. Open the "SampleScene" Scene
3. Open "TestGraph" in Assets folder to see a "GameObjectNode"
4. Assign a GameObject from the Scene to the Node's Option and save the “TestGraph”
5. Open the “NewScene” Scene
6. Open the “SampleScene” Scene
7. Observe the results in “TestGraph” window

Actual Result: The GameObject is successfully assigned, but will eventually be unreferenced when the GameObject is unloaded
Expected Result: Scene object references should be rejected as "Type mismatch"

Reproducible with: 0.1.0-exp.1 (6000.2.0a9), 0.4.0-exp.2 (6000.2.0a9), 6000.5.3f1, 6000.6.0b2, 6000.7.0a2
Could not test with: 0.4.0-exp.2 (6000.3.19f1) (I had a crash when I was trying to add the “GameObjectNode”)

Reproducible on: Windows 11 Enterprise (25H2)
Not reproducible on: No other environments tested

Note: The assignment is also removed after the Editor is closed or reopened