Comment 2 for bug 1579693

On selecting System...
freds@multivac16:~$ sysinfo
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.Gnome () <0xaec83fb0 + 0x00070> in <filename unknown>:0
  at Sysinfo.Sysinfo.on_notebook1_switch_page (System.Object o, Gtk.SwitchPageArgs e) <0xaec7e000 + 0x00147> in <filename unknown>:0
  at Gtk.Notebook.SwitchPageSignalCallback (IntPtr arg0, IntPtr arg1, UInt32 arg2, IntPtr gch) <0xb1412a58 + 0x00251> in <filename unknown>:0
  at GLib.ExceptionManager.RaiseUnhandledException (System.Exception e, Boolean is_terminal) [0x00000] in <filename unknown>:0
  at Gtk.Notebook.SwitchPageSignalCallback (IntPtr arg0, IntPtr arg1, UInt32 arg2, IntPtr gch) [0x00000] in <filename unknown>:0
  at Gtk.Notebook.gtk_notebook_set_current_page (IntPtr , Int32 ) [0x00000] in <filename unknown>:0
  at Gtk.Notebook.set_CurrentPage (Int32 value) [0x00000] in <filename unknown>:0
  at Sysinfo.Sysinfo.on_treeview1_cursor_changed (System.Object o, System.EventArgs e) [0x00000] in <filename unknown>:0
  at System.Reflection.MonoMethod.InternalInvoke (System.Reflection.MonoMethod , System.Object , System.Object[] , System.Exception& ) [0x00000] in <filename unknown>:0
  at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <filename unknown>:0
  at System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) [0x00000] in <filename unknown>:0
  at System.Delegate.DynamicInvokeImpl (System.Object[] args) [0x00000] in <filename unknown>:0
  at System.MulticastDelegate.DynamicInvokeImpl (System.Object[] args) [0x00000] in <filename unknown>:0
  at System.Delegate.DynamicInvoke (System.Object[] args) [0x00000] in <filename unknown>:0
  at GLib.Signal.ClosureInvokedCB (System.Object o, GLib.ClosureInvokedArgs args) [0x00000] in <filename unknown>:0
  at GLib.SignalClosure.Invoke (GLib.ClosureInvokedArgs args) [0x00000] in <filename unknown>:0
  at GLib.SignalClosure.MarshalCallback (IntPtr raw_closure, IntPtr return_val, UInt32 n_param_vals, IntPtr param_values, IntPtr invocation_hint, IntPtr marshal_data) [0x00000] in <filename unknown>:0
  at Gtk.Application.gtk_main () [0x00000] in <filename unknown>:0
  at Gtk.Application.Run () [0x00000] in <filename unknown>:0
  at Sysinfo.Sysinfo..ctor (System.String[] args) [0x00000] in <filename unknown>:0
  at Sysinfo.Sysinfo.Main (System.String[] args) [0x00000] in <filename unknown>:0
freds@multivac16:~$