Steps to reproduce:

1) Run HelloSanity

2) Click on the "Windows" button to bring up the Windows Demo panel

Note that the "Resize ..." and "Minimize" buttons are disabled (as they should be)

3) Click on the "Open new window" button

A window will be created and the "Resize ..." and "Minimize" buttons are enabled (as they should be), and they function properly

4) Close the other window by pressing the red X in the window decoration

The "Resize..." and "Minimize" buttons are still active, but no longer do anything. This is confusing so the buttons should be disabled when the other window is closed.