xfce4-panel freezes if a window closes while its taskbar menu is open

System Information:

• Debian 13 (trixie)
• xfce4-panel 4.20.4 (Xfce 4.20)
• GTK 3.24.49
• Kernel 6.12.32-amd64
• X11

Steps to reproduce:

1. Open a new terminal window.
2. Run command sleep 10 ; exit
3. Right click the window's entry on the panel's taskbar to bring up its menu.
4. Wait for the terminal window to close itself.
5. The open menu should become transparent and the panel will become unresponsive.

If running from a terminal then the following error message will occur repeatedly:

'WIDGET_REALIZED_FOR_EVENT (widget, event)' failed

• The frozen panel will update its display when the active workspace changes and will respond to changes made in the Panel Preferences window, but it will not respond to user input.
• If more than one panel is open then the other panels are not affected.
• Normal operation can be restored by running xfce4-panel -r from the Application Finder.