gui: prevent error messages at start-up (regression from changeset 6c0fce0632a4) * main-window.h: declaration of new function connect_visibility_changed () * main-window.cc (connect_visibility_changed): new function for connecting the signales emitted when the visibility of a widget changes; this function must be called after the main window is shown * main-window.cc (construct): do not connect the signals here * octave-gui.cc (octave_start_gui): call connect_visibility_changed () just before calling application.exec ()

--- a/libgui/src/main-window.h
+++ b/libgui/src/main-window.h
@@ -123,6 +123,7 @@
 
   void read_settings ();
   void write_settings ();
+  void connect_visibility_changed ();
 
 protected:
   void closeEvent (QCloseEvent * closeEvent);