In every settings window : Gtk-WARNING **: Content added to the action area of a dialog using header bars

Hi,

Since version 4.16 (Arch up to date) I have these warnings by opening settings windows doesn't matter which one as you can see :

`(xfce4-session-settings:4706): Gtk-WARNING **: 12:25:52.777: Content added to the action area of a dialog using header bars

(xfce4-session-settings:4706): Gtk-WARNING **: 12:25:52.778: Content added to the action area of a dialog using header bars

(xfce4-mouse-settings:4712): Gtk-WARNING **: 12:26:02.653: Content added to the action area of a dialog using header bars

(xfce4-mouse-settings:4712): Gtk-WARNING **: 12:26:02.654: Content added to the action area of a dialog using header bars

(xfce4-power-manager-settings:6373): Gtk-WARNING **: 13:31:47.204: Content added to the action area of a dialog using header bars

(xfce4-power-manager-settings:6373): Gtk-WARNING **: 13:31:47.205: Content added to the action area of a dialog using header bars

(xfce4-appearance-settings:1666): Gtk-WARNING **: 11:42:19.294: Content added to the action area of a dialog using header bars

(xfce4-appearance-settings:1666): Gtk-WARNING **: 11:42:19.295: Content added to the action area of a dialog using header bars

(wrapper-2.0:1122): Gtk-WARNING **: 13:30:48.575: Content added to the action area of a dialog using header bars`

What's that ?

Thank you.