can't empty the data of the table

Hello, I'm trying to empty the array of the table. But I cannot. I'm using mode: 'external' and when the data arrives from webservice if it's empty I do:

```
this.data.length = 0;
this.source.empty()
```

I tried also `this.data = []` but it doesn't work either.

The data source is:` this.source = new LocalDataSource(this.data);` I know I made if local but the object is local, I just do webservice calls on events.