area with missing plot tutorial - google charts examples

Code

<html>
<head>
<title>Google Charts tutorial Tutorial</title>
   <script type="text/javascript" src="https://www.gstatic.com/charts/loader.js"></script>
   <script type="text/javascript">
     google.charts.load('current', {packages: ['corechart']});     
   </script>
</head>
<body>
<div id="container" style="width: 550px; height: 400px; margin: 0 auto"></div>
<script language="JavaScript">
function drawChart() {
   // Define the chart to be drawn.
   var data = google.visualization.arrayToDataTable([
      ['Year', 'Asia', 'Europe'],
	  ['2012',  900,      390],
      ['2013',  1000,      400],
      ['2014',  1170,      null],
      ['2015',  1250,       480],
      ['2016',  1530,      540]
      ]);
   var options = {
      title: 'Population (in millions)',
      hAxis: {
         title: 'Year',  
         titleTextStyle: {
            color: '#333'
         }
      },
      vAxis: {
         minValue: 0
      }
   };

// Instantiate and draw the chart.
   var chart = new google.visualization.AreaChart(document.getElementById('container'));
   chart.draw(data, options);
}
google.charts.setOnLoadCallback(drawChart);
</script>
</body>
</html>

Result