title: NVD3.js MultiChart with area (stackedArea) series drawn below the x-axis obscures labels
body: <p>Hello I'm using the current nvd3.js multichart from GitHub master branch. A certain combination of values is causing my chart to draw the area series below the x-axis, causing the series to obscure the x-axis labels when the chart is zoomed in. </p>
  
  <p><a href="https://i.stack.imgur.com/6Stdr.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/6Stdr.png" alt="enter image description here"></a></p>
  
  <p>When zoomed in it looks like this.</p>
  
  <p><a href="https://i.stack.imgur.com/F2tWj.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/F2tWj.png" alt="enter image description here"></a></p>
  
  <p>This example is here <a href="https://github.com/mlawry/nvd3/blob/master/examples/multiChart4.html" rel="nofollow noreferrer">https://github.com/mlawry/nvd3/blob/master/examples/multiChart4.html</a>
  Just place the file "multiChart4.html" in the "examples" folder of an nvd3 Git repository and open it in any Web browser.</p>
  
  <p>The funny thing is this doesn't always happen, only with certain values. Can anyone point me in the right direction to fix this problem?</p>