Shorter steps to reproduce:

- Import the project
- Try to open sprite editor

Note Changing layout gives you error in the console and clears out the orphaned window. After this everything works fine.

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Steps to reproduce :

- import the project attached
- open a new scene and add the bus, flame and bomb sprite to the scene
- scale all 3 sprites
- press ctrl+z to scale them back to the original
- select the cab in the Project Browser
- click on the Sprite Editor and notice it does not open

Note:
Reproed on 4.3RC2.