Shortcut key to close diff popup window?

Hi,

IIJ might be the best tool I've found for comparing git branches but for one glaring flaw.  I can:

1) Open the list of files to diff.

2) Begin the file diff via Ctrl-D

3) Navigate the file via F7 and Shift-F7

... but then, I need to click the OS X red button to close the diff window.  There is no shortcut to close the window. Command-W (or the options I've tried in the Keymap table) doesn't appear work. 

This doesn't seen optimal given there is a shortcut to open the same window.  https://devnet.jetbrains.com/message/5522041 appears to point to an issue with a similar window.

Any chance this might make it into an upcoming release?

Thanks!