Multiple Preferences windows can be opened

[aliaksandrsen]

I noticed an issue with the Preferences window. If I open Preferences, then minimize the window, and later select Preferences again from the menu bar icon, a new Preferences window opens instead of restoring the existing one. This can be repeated multiple times, resulting in several Preferences windows open simultaneously.

Expected behavior: only a single instance of the Preferences window should exist, and selecting Preferences again should bring the existing window to the foreground.

Steps to reproduce:

1. Open Preferences
2. Minimize the Preferences window
3. Click the app icon in the menu bar
4. Open Preferences again
5. Observe that a new window appears

Thank you for looking into this.