This wasn't added on the GObject-ification in commit c4c5c4fd5c. This introduced warnings and misbehaviors when closing the dialog. (Eg. pressing the "show OSD" pad action would show stack different dialogs on top each other). https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/800
GNOME Shell
GNOME Shell provides core user interface functions for the GNOME 3 desktop, like switching to windows and launching applications. GNOME Shell takes advantage of the capabilities of modern graphics hardware and introduces innovative user interface concepts to provide a visually attractive and easy to use experience.
For more information about GNOME Shell, including instructions on how to build GNOME Shell from source and how to get involved with the project, see the project wiki.
Bugs should be reported to the GNOME bug tracking system.
Contributing
To contribute, open merge requests at https://gitlab.gnome.org/GNOME/gnome-shell.
Commit messages should follow the GNOME commit message guidelines. We require an URL to either an issue or a merge request in each commit.
License
GNOME Shell is distributed under the terms of the GNU General Public License, version 2 or later. See the COPYING file for details.