Fix the issue where the tagsList in Histogram will return undefined items. (#250)

Author: jetfuel

frontend/src/histogram/Histogram.san

@@ -62,7 +62,7 @@ export default {
  run,
  tag: tags[run][tag]
  };
- });
+ }).filter(item => item.tag !== undefined);
  return {
  tagList,
  tag,

frontend/src/scalars/ui/chart.san

@@ -129,6 +129,7 @@ export default {
  this.data.set('downloadType', runsItems[0].value);
  },
 
+ // Create a Scalar Chart, initialize it with default settings, then load datas
  initChart(tagInfo) {
  this.createChart();
  this.setChartsOptions(tagInfo);
@@ -141,6 +142,7 @@ export default {
  },
 
  setChartsOptions({tagList, tag}) {
+ // Create two lines, one line is original, the other line is for smoothing
  let seriesOption = tagList.map(item => [
  {
  name: item.run,