customTooltips not working properly

When setting customTooltips like in Chart.js, an event is triggered only when a cursor hovers the dot. Please see this example:

``` javascript
customTooltips: function(tooltip) {
   if(!tooltip) {
      $('#tooltip').hide(); //code never executed
   }
   $('#tooltip').html(tooltip.text);
   $('#tooltip').show();
}
```

Thats why my custom tooltips allways remain visible...
