title: Hiding label guidelines on Highcharts pie charts
body: <p>In Highcharts, I've been using the dataLabel formatter to return an empty string value for zero values.  This effectively hides the label for zero values.  However, on pie charts, there is a guideline that points to each pie slice, even if the slice has a zero value. I can't seem to remove these guidelines without directly manipulating the DOM elements.  I'd like to keep the empty pie slices in the chart because I am dynamically updating the chart based on user-manipulated filter criteria, but I would like to hide the guidelines pointing to empty pie slices.</p>
  
  <p>Does anyone know of a way to configure Highcharts remove the guidelines pointing to empty pie slices?  I am able clear out the label itself using the formatter below:</p>
  
  <pre><code>formatter: function ()
  {
     var y = this.y;
     if (y == 0)
       return "";
     ...
  }
  </code></pre>