Shell's WindowTracker switched to those signals instead of tracking windows through MetaWorkspace's window-added/removed signals. As ::window-created is only emitted after a window has been added to its workspace, looking up its app on ::window-added now fails because the window isn't tracked yet. Address this by switching to the same signals for window tracking (which is simpler anyway). https://gitlab.gnome.org/GNOME/gnome-shell-extensions/-/issues/372