if we set a new stock_id and there was a previous stock_id, unref the

if we set a new stock_id and there was a previous stock_id, unref the

Wed Dec 17 23:50:56 2003  Kristian Rietveld  <kris@gtk.org>

	* gtk/gtkcellrendererpixbuf.c (gtk_cell_renderer_pixbuf_set_property):
	if we set a new stock_id and there was a previous stock_id, unref
	the pixbuf (since it was used to renderer the previous stock_id
	and stock_id might have been set to NULL now). (Fixes #122966).