don't mark a RefExpProxy during bubble if it's already dirty
don't mark a RefExpProxy during bubble if it's already dirty

marcalexiei/ractive,ractivejs/ractive,ractivejs/ractive,ISNIT0/ractive,ractivejs/ractive,marcalexiei/ractive,ISNIT0/ractive,marcalexiei/ractive,ISNIT0/ractive