Uncaught TypeError: Cannot read property 'data' of null when loading data on donut chart

I get this error when moving my mouse on a donut chart that is in the process of loading data:
`Uncaught TypeError: Cannot read property 'data' of null c3.js:4695`
It looks like the tooltip is trying to be drawn while data is being loaded, and this error is thrown because the data (d) is not ready yet.

Except from c3.js:4695:

``` javascript
c3_chart_internal_fn.convertToArcData = function (d) {
return this.addName({
id: d.data.id,
value: d.value,
ratio: this.getArcRatio(d),
index: d.index
});
};
```

Can you stop the drawing of tooltips while data is being loaded?