title: HighCharts Heatmap: Plotting error with >= 1024 samples
body: <p>I'm creating HighCharts heatmaps with lots of samples. When I try to create a plot with 32 x 32 samples, I get lots of spurious empty y-categories created.</p>
  
  <p>No problem with 31 x 32 heatmap: <a href="http://jsfiddle.net/tallphil/8xattd5s/" rel="nofollow noreferrer">http://jsfiddle.net/tallphil/8xattd5s/</a></p>
  
  <p>32 x 32 heatmap breaks: <a href="http://jsfiddle.net/tallphil/fr43pqmb/" rel="nofollow noreferrer">http://jsfiddle.net/tallphil/fr43pqmb/</a></p>
  
  <p>Any ideas what could be going on here? My suspicion is that HighCharts is doing something weird when it hits the magical 1024 sample number.</p>
  
  <p>Many thanks in advance,</p>
  
  <p>Phil</p>
  
  <p><em>ps. Stack Overflow insists that I paste some code here because I used a jsfiddle link, so here's the plotting code without the data:</em></p>
  
  <pre><code>Highcharts.chart('container', {
    chart: { type: 'heatmap' },
    title: { text: 'Heatmap Test' },
    colorAxis: {
      min: 0,
      minColor: '#FFFFFF',
      maxColor: Highcharts.getOptions().colors[0]
    },
    series: [{
      name: 'Sales per employee',
      borderWidth: 1,
      data: DATA_HERE
    }]
  });
  </code></pre>