Your system information

• Steam client version (build number or date): May 18, 14:50:44 / 1526683293
• Distribution (e.g. Ubuntu): Debian testing
• Opted into Steam client beta?: No
• Have you checked for system updates?: Yes
• i3 version 4.15

Operating System Version:
Debian GNU/Linux testing (buster) (64 bit)
Kernel Name: Linux
Kernel Version: 4.16.0-1-amd64
X Server Vendor: The X.Org Foundation
X Server Release: 11906000
X Window Manager: i3
Steam Runtime Version: steam-runtime-beta-release_2017-10-05

Please describe your issue in as much detail as possible:

When closing any steam window via Win+Shift+q I get the "Steam is shutting down" window and steam quits. This happens always, even when there are plenty other steam windows open.
From man i3: Kills the current window. This is equivalent to "clicking on the close button", meaning a polite request to the application to close this window. For example, Firefox will save its session upon such a request. If the application does not support that, the window will be killed and it depends on the application what happens.

I'd expect the window to close like when pressing the X in the top right corner.

This is probably related to: #53 #5157 #5433 #2685

Steps for reproducing this issue:

1. Open Steam
2. Open any window from steam (friendlist, messages, main window, ...)
3. Use WM to close the window (here: i3)