black window drawn on second display with 0 alpha blacks out Mission Control preview

This is an issue observed on Mac OS X versions 10.8 and 10.9

Steps to reproduce:

1. Have a multi-monitor setup of at least two displays.
2. Play a video and take it full screen. Primary display shows video. Secondary display gets black window overlay.
3. Exit full screen. Everything looks normal. But black window on secondary display is still there with 0 alpha.
4. Enter Mission Control. Mission Control preview of previously blacked-out space remains black, even though that space is actually not hidden by the 0 alpha black window.

The black window should not be left open covering the secondary display when out of full screen mode.