Brush (lineX, lineY) selection values are not available with line charts

### Version
5.0.2

### Reproduction link
[https://codepen.io/tamersalama/pen/mdOraGb?editors=1111](https://codepen.io/tamersalama/pen/mdOraGb?editors=1111)

### Steps to reproduce
1- Create a *line* chart with a horizontal selector (lineX) brush

2- Use the brush to select a data range

3- The onbrushselected event fires up normally, however the event parameters' dataIndex (`params.batch[0].selected[0].dataIndex`) returns an empty array

4- Changing the chart type to scatter or bar will result in a proper dataIndex being returned

### What is expected?
It's expected that the `dataIndex` for the selection to have an array of selected values

### What is actually happening?
dataIndex within `params.batch[0].selected[0].dataIndex` is empty