This patch aims to improve user experience by not allowing the user to drag and drop a folder into itself.
The current behavior shows a red message at the top which can then be closed by the user, instead of relying on that, this patch disables the option of dropping onto self and uses the "Invalid drop target cursor" to highlight the behavior.
BUG: 307747
Since spectacle is unable to screenshot the cursor overlay, find attached a photo of the screen.