Fix a bug when the opacity/fill/stroke for bars is not defined.
Fix a bug when the opacity/fill/stroke for bars is not defined.

jameskraus/react-vis,uber-common/react-vis,Apercu/react-vis,Apercu/react-vis,uber-common/react-vis,Apercu/react-vis,uber/react-vis,uber/react-vis,uber/react-vis,jameskraus/react-vis