Improperly added new row when using virtualDataSource

[Svetoslavb04]

Describe the bug
The new row is not added to the top and it is filled with improper data when using virtualDataSource.
In the example, the row should only have an id with the length of the total rows and should be added to the top.

To Reproduce
Steps to reproduce the behaviour:

1. Go to https://jsfiddle.net/vz2w1top/2/
2. Click on 'Add' a few times
3. See an error

Expected behaviour
Expected a new row to be added to the top