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/status/rfkill.js

@@ -15,15 +15,15 @@ const rfkillManagerInfo = Gio.DBusInterfaceInfo.new_for_xml(RfkillManagerInterfa
 const RfkillManager = GObject.registerClass({
     Properties: {
         'airplane-mode': GObject.ParamSpec.boolean(
-            'airplane-mode', '', '',
+            'airplane-mode', null, null,
             GObject.ParamFlags.READWRITE,
             false),
         'hw-airplane-mode': GObject.ParamSpec.boolean(
-            'hw-airplane-mode', '', '',
+            'hw-airplane-mode', null, null,
             GObject.ParamFlags.READABLE,
             false),
         'show-airplane-mode': GObject.ParamSpec.boolean(
-            'show-airplane-mode', '', '',
+            'show-airplane-mode', null, null,
             GObject.ParamFlags.READABLE,
             false),
     },