Google Charts Area Chart with missing points

Google Charts Area Chart with missing points

<html>
   <head>
      <title>Google Charts 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>