X64 client, and X close box on MDI Window

I’ve just begun to roll out X64 client v17 to my users. (17.1)
We’ve discovered that when the user clicks the X-close box on the main MDI window, nothing happens.
In x32, clicking on the MDI x close box triggers a file-quit.

Is this a bug?
Is this documented?

The answer is http://forums.4d.com/Post/FR/15196773/1/15199491#15200659Here>
But there is a new bug also https://forums.4d.com/Post/FR/25911868/0/0/here> (sorry in French) There is a problem with the On Exit database method

Thank you Manuel: that fixed it for me!