message: fix index error for bar charts
diff: @@ -1142,7 +1142,7 @@ class DistributionBarViz(DistributionPieViz):
  d = {
  "key": series_title,
  "values": [
  - {'x': str(row.index[i]), 'y': v}
  + {'x': str(i), 'y': v}
  for i, v in ys.iteritems()]
  }
  chart_data.append(d)
  