Use NULL for nick/blurb in GObject params

As they are only used by gstreamer for gst-inspect & other tools.
Projects like Mutter/gtk have completely dropped them as well, so follow
their path

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3505>

js/ui/modalDialog.js

@@ -25,7 +25,7 @@ export const State = {
 export const ModalDialog = GObject.registerClass({
     Properties: {
         'state': GObject.ParamSpec.int(
-            'state', 'Dialog state', 'state',
+            'state', null, null,
             GObject.ParamFlags.READABLE,
             Math.min(...Object.values(State)),
             Math.max(...Object.values(State)),