message: Fix GroupAvatar crash
  When we don't have an avatar we shouldn't explode.
diff: @@ -39,6 +39,7 @@ export default class GroupAvatar extends React.Component<IProps> {
  };
  getGroupAvatarUrl() {
  + if (!this.props.groupAvatarUrl) return null;
  return mediaFromMxc(this.props.groupAvatarUrl).getThumbnailOfSourceHttp(
  this.props.width,
  this.props.height,
  