How to reproduce:

1. Open HUB;
2. Create 3D(HDRP) project;
3. Create visual effect graph in the "Project" window (Create->Visual Effects-> Visual Effect Graph);
4. Drag it to the "Hierarchy" window;
5. Select it in the “Hierarchy” window;
6. Go to “Inspector” window and click “Edit” in the “General” section;
7. Verify, that VFX window opens and it displays graph and blackboard is displayed by default on top;
8. Go to “Hierarchy” window and delete your created VFX;
9. Go to “Project” window and delete VFX asset too;
10. Close the project and save the changes;
11. Open the same project again.

Expected result: 

1. "No Asset" window shouldn't be displayed in this case, because it is empty (all VFX were deleted).
2. If "No Asset" window should be displayed, so in this case "Blackboard" button should be enabled that user could hide it from his screen.

Actual result: "No Asset" window is presented. Blackboard window by default displayed on top. And its button is disabled (there is no opportunity to remove it from the screen).

Reproducible with: 10.10.0 (2020.3.41f1), 12.1.7 (2021.3.12f1), 13.1.8 (2022.1.21f1),  14.0.3 (2022.2.0b12), 15.0.1 (2023.1.0a16).