A canvas panel is created for blank widgets when reopening the editor

A canvas panel is created for blank widgets when reopening the editor. The canvas panel returns when the editor is restarted if the widget is empty

1. Open the editor
2. Create a new widget blueprint
3. Delete the canvas panel
4. Save and compile
5. Close the editor
6. Reopen the same project
7. Reopen the widget that was created
8. Notice that the canvas panel is back

Expected: The canvas panel would no longer be present after it has been deleted
Result: The canvas panel returns when the editor is restarted if the widget is empty