Broken: 2.80 7c438e5366b
Short description of error
If the windows close box is clicked multiple times a prompt quit dialog is created each time. This leads to multiple clicks needed to dismiss them before blender quits.
Exact steps for others to reproduce the error
Enable prompt quit and move the default cube, then click the windows close box multiple times.
The front most dialog can be moved, in the example image I have moved each one before clicking the close widget again.