window_removed
Description:
Emitted when a Window is removed from application, either as a side-effect 
      of being destroyed or explicitly through remove_window.
Parameters:
| window | 
           the Window that is being removed  | 
      
Emitted when a Window is removed from application, either as a side-effect 
      of being destroyed or explicitly through remove_window.
| window | 
           the Window that is being removed  |