Steps to reproduce
- Run the attached project
- Click on the first DropDownList, leave it open
- Click on the second DropDownList multiple times
Actual result: the DropDownController of the first list, which has been removed from stage, is still listening to MouseEvent.MOUSE_DOWN and SandboxMouseEvent.MOUSE_DOWN_SOMEWHERE on SystemManager.
Expected result: the DropDownController of the first list stops listening to events.