UCS continuously runs while a blueprint's thumbnail in content browser is focused

Blueprints with a mesh call the UCS continuously when focusing the thumbnail in the content browser.

This is easily visible with a Print String in the UCS causing log spam.

This does not occur in 4.11.2

1. In a new Blueprint project create a new Actor blueprint
2. Open the blueprint and focus the construction script
3. Connect a Print String node to the construction script
4. In the My Blueprint panel add a Cube mesh component
5. Compile and save the blueprint
6. Close the blueprint editor
7. Open the Output log and focus the content browser

Result: The print string from the construction script is continuously running as long as the Editor (not a sub editor) is focused.