On a dual monitor system, clicking a blank area of the panel can sometimes close an application

Using a dual monitor:

1. Open an application window, e.g. gedit.
2. Maximise the application on one monitor. Moving the mouse to the panel on that monitor reveals the menus and window buttons as expected. Moving the mouse to the panel on the other monitor does nothing, as expected.
3. Click on the panel on the second monitor in the top left area. This area is blank, but is where a close button would be.

What I expect to happen:
4. Nothing

What happens:
4. The application closes.

unity:
  Installed: 4.24.0-0ubuntu2b1
  Candidate: 4.24.0-0ubuntu2b1
  Version table:
 *** 4.24.0-0ubuntu2b1 0
        500 http://archive.ubuntu.com/ubuntu/ oneiric-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     4.22.0-0ubuntu3 0
        500 http://archive.ubuntu.com/ubuntu/ oneiric/main amd64 Packages