Add a destroy implementation in order to set priv->cell_view to NULL

Add a destroy implementation in order to set priv->cell_view to NULL

Tue Feb 24 01:08:27 2004  Matthias Clasen  <maclas@gmx.de>

	* gtk/gtkcombobox.c: Add a destroy implementation in order to
	set priv->cell_view to NULL before finalize stumbles over the
	dangling pointer. This big array of pointers into the widget
	tree in GtkComboBoxPrivate is really fragile and should be
	cleaned up.