Exception in Gtk# callback delegate
  Note: Applications can use GLib.ExceptionManager.UnhandledException to handle the exception.
System.NullReferenceException: Object reference not set to an instance of an object
  at Sysinfo.SystemInfo.Xorg () [0x00000] in <filename unknown>:0 
  at Sysinfo.Sysinfo.on_notebook1_switch_page (System.Object o, Gtk.SwitchPageArgs e) [0x00000] in <filename unknown>:0 
  at Gtk.Notebook.SwitchPageSignalCallback (IntPtr arg0, IntPtr arg1, UInt32 arg2, IntPtr gch) [0x00000] in <filename unknown>:0 
   at GLib.ExceptionManager.RaiseUnhandledException(System.Exception e, Boolean is_terminal)
   at Gtk.Notebook.SwitchPageSignalCallback(IntPtr arg0, IntPtr arg1, UInt32 arg2, IntPtr gch)
   at Gtk.Notebook.gtk_notebook_set_current_page(IntPtr , Int32 )
   at Gtk.Notebook.set_CurrentPage(Int32 value)
   at Sysinfo.Sysinfo..ctor(System.String[] args)
   at Sysinfo.Sysinfo.Main(System.String[] args)