Incorrect behavior on macOS when closing the window

[vincentisambart]

Describe the bug

• On macOS, closing the window should not change the active app to another app.

To Reproduce

• Open Zulip.
• Close the window (for example with Cmd+W).

Expected behavior

• The active app should still be Zulip.

Screenshots

Desktop (please complete the following information):

• Operating System: macOS 11.4
• Zulip Desktop Version: 5.7.0

Additional context

• Due to that non-standard behavior, I ended up closing by mistakes other apps when I wanted to close Zulip (doing Cmd+W followed by a Cmd+Q).
• I know about the setting to close the app when closing the window, but I sometimes I just close the window to remove clutter, and then later come back to read the unread messages left.