Fix variable to get widget settings

[City-busz]

This caused the panel to freeze when the cursor blink time was changed.

The console output was:

(lxpanel:57939): Gtk-CRITICAL **: 20:17:59.216: gtk_widget_get_settings: assertion 'GTK_IS_WIDGET (widget)' failed

(lxpanel:57939): GLib-GObject-CRITICAL **: 20:17:59.216: g_object_get: assertion 'G_IS_OBJECT (object)' failed