Follow-up from "ChatControlBase: Rework drag and drop"
The following discussion from !556 (merged) should be addressed:
does not work for me on Ubuntu for some reason
and i get this error on closing the chat control
(gajim:6237): Gtk-WARNING **: 23:07:10.491: Can't set a target list on a widget until you've called gtk_drag_dest_set() to make the widget into a drag destination