title: Highcharts - updating series leads to tooltip-related error (mouseOver)
body: <p>As can be seen <a href="http://jsfiddle.net/43ygghz3/1/" rel="nofollow">in this simple fiddle,</a> triggering the mouseOver event on a data point and updating the series' properties via <code>series.update()</code> leads to a js error:</p>
  
  <pre><code>Uncaught TypeError: Cannot read property 'tooltipOptions' of null
  </code></pre>
  
  <p>The code:</p>
  
  <pre><code>plotOptions: {
           series: {
               cursor: 'pointer',
               point: {
                   events: {
                       mouseOver: function () {
                           console.log('why does an error appear?');
                           this.series.update({
                               lineWidth: 10
                           });
                       },
                       mouseOut: function () {
                           console.log('bla');
                       }
                   }
               }
           }
       },
  </code></pre>
  
  <p>What have I done wrong? Thanks for info.</p>
  
  <p>When setting the tooltip to <code>enabled: false</code>, the error message is:</p>
  
  <pre><code>Uncaught TypeError: object is not a function highcharts.js:300
    r.onMouseOver                              highcharts.js:300
    Wa.runPointActions                         highcharts.js:158
    Wa.onContainerMouseMove                    highcharts.js:165
    b.onmousemove                              highcharts.js:167
  </code></pre>