title: Highcharts / HighStock issue, series disappearing on dynamic update
body: <p>I have this high stocks area chart, consuming a JSON api.  Each n seconds, the chart recalls the API for the delta in points.</p>
  
  <p>After a few minutes, the left hand side series disappears, however, if you mouse over it, the labels still appear. Happens on Mac and Windows, FF IE Chrome and Safari.  Would appreciate any help.</p>
  
  <p>You can view a demo here:</p>
  
  <p><a href="https://dev-mv-charts.azurewebsites.net/goldarea.htm" rel="nofollow">https://dev-mv-charts.azurewebsites.net/goldarea.htm</a></p>
  
  <p>Update:  If I use the below code, take from the highcharts site, it seems to work.  Just need to replace the initial load of random data now.</p>
  
  <pre><code>$(function () {
  
  Highcharts.setOptions({
      global : {
          useUTC : true
      }
  });
  
  // Create the chart
  $('#container').highcharts('StockChart', {
      chart : {
          events : {
              load : function () {
  
                  // set up the updating of the chart each second
                  var series = this.series[0];
                  setInterval(function () {
  
                      var _update_url = 'http://api.bullionmark.com/v1/ask?currencyId=2&amp;commodityId=1';
  
                      $.ajax({
                          type: 'GET',
                          url: _update_url}).done(function (resp1) {
  
                              var x2 = parseInt(resp1.Timestamp) * 1000;
                              var y2 = parseFloat(resp1.Current);
  
                              //var x = (new Date()).getTime(), // current time
                              //y = Math.round(Math.random() * 100);
  
                              series.addPoint([x2, y2], true, true);
  
                          });
  
                  }, 5000);
              }
          }
      },
  
      rangeSelector: {
          buttons: [{
              count: 1,
              type: 'minute',
              text: '1M'
          }, {
              count: 5,
              type: 'minute',
              text: '5M'
          }, {
              type: 'all',
              text: 'All'
          }],
          inputEnabled: false,
          selected: 0
      },
  
      title : {
          text : 'Live random data'
      },
  
      exporting: {
          enabled: false
      },
  
      series : [{
          name : 'Random data',
          type : 'area',
          data : (function () {
              // generate an array of random data
              var data = [], time = (new Date()).getTime(), i;
  
              for (i = -999; i &lt;= 0; i += 1) {
                  data.push([
                      time + i * 1000,
                      Math.round(Math.random() * 100)
                  ]);
              }
              return data;
          }())
      }]
  });
  
  });
  </code></pre>