title: ZedGraph PointPairs only 1 symbol
body: <p>I'm hoping someone may have the answer to this one</p>
  
  <p>I've added some "PointPair" values to a ZedGraph graph, and this all works fine.  However, when I show Symbols, it only shows the symbol on the high value, not the low value.</p>
  
  <p>Does anyone know what could be causing this?</p>
  
  <p><strong>EDIT - Code Sample</strong> (sorry, I should've put this on yesterday)</p>
  
  <pre><code>// GraphPane pane (field)
  
  FilledLineItem filledLineItem = new FilledLineItem("myline", upperPoints, lowerPoints, Color.DodgerBlue, ZedGraph.SymbolType.Square)
  pane.CurveList.Add(filledLineItem);
  </code></pre>
  
  <p>Where upperPoints and lowerPoints are of type PointPairList</p>