Comment 4 for bug 1712798

The issue is with one of the gnome-shell ubuntu changes

+ let schema = source.lookup('com.ubuntu.sound', true);
+ if (schema) {
+ this._volumesettings = new Gio.Settings({ settings_schema: schema });
+ }
+
+ this._volumesettings.connect

or this._volumesettings is undefined if the schemas is not installed and the code errors out