Only one legend item if no data outlier

<!DOCTYPE html>
<html>

<head>
  <meta charset="utf-8">
  <title>ZingSoft Demo</title>

  <script nonce="undefined" src="https://cdn.zingchart.com/zingchart.min.js"></script>
  <style></style>
</head>

<body>
  <div id='myChart'></div>
  <script>
    ZC.LICENSE = ["569d52cefae586f634c54f86dc99e6a9", "b55b025e438fa8a98e32482b5f768ff5"];
    var myConfig = {
      "graphset": [{
          "type": "boxplot",
          "legend": {},
          /* Objects omitted for brevity */
          "series": [{
            "data-box": [
              [760, 801, 848, 895, 965],
              [733, 853, 939, 980, 1080],
              /* Arrays omitted for brevity */
            ],
            "data-outlier": [
              [0, 644],
              [1, 718],
              /* Arrays omitted for brevity */
            ]
          }]
        },
        {
          "type": "boxplot",
          "legend": {},
          /* Objects omitted for brevity */
          "series": [{
            "data-box": [
              [760, 801, 848, 895, 965],
              [733, 853, 939, 980, 1080],
              /* Arrays omitted for brevity */
            ],
          }]
        }
      ]
    };

    zingchart.render({
      id: 'myChart',
      data: myConfig,
      height: 400,
      width: 600
    });
  </script>
</body>

</html>

<!DOCTYPE html>
<html>

<head>
  <meta charset="utf-8">
  <title>ZingSoft Demo</title>

  <script src="https://cdn.zingchart.com/zingchart.min.js"></script>
</head>

<body>
  <div id='myChart'></div>
</body>

</html>

var myConfig = {
  "graphset": [{
      "type": "boxplot",
      "legend": {},
      /* Objects omitted for brevity */
      "series": [{
        "data-box": [
          [760, 801, 848, 895, 965],
          [733, 853, 939, 980, 1080],
          /* Arrays omitted for brevity */
        ],
        "data-outlier": [
          [0, 644],
          [1, 718],
          /* Arrays omitted for brevity */
        ]
      }]
    },
    {
      "type": "boxplot",
      "legend": {},
      /* Objects omitted for brevity */
      "series": [{
        "data-box": [
          [760, 801, 848, 895, 965],
          [733, 853, 939, 980, 1080],
          /* Arrays omitted for brevity */
        ],
      }]
    }
  ]
};

zingchart.render({
  id: 'myChart',
  data: myConfig,
  height: 400,
  width: 600
});