Check that the fontsel has a screen assigned before doing anything. This

Check that the fontsel has a screen assigned before doing anything. This

2006-02-27  Federico Mena Quintero  <federico@novell.com>

	* gtk/gtkfontsel.c (gtk_font_selection_set_font_name): Check that
	the fontsel has a screen assigned before doing anything.  This
	will at least warn the caller of what is wrong, since we only
	populate the family_list until we get a screen.  Also, put the
	reference docs here.  Fixes bug #332756.
	(gtk_font_selection_dialog_get_font_name): Document this here.
	(gtk_font_selection_get_font_name): Document this here; mention
	that the font names get normalized, so the result of this function
	may not be the same as what you set with
	gtk_font_selection_set_font_name().