This bug is present on this Demo that you provide, 

http://demos.telerik.com/aspnet-ajax/grid/examples/data-editing/batch-editing/defaultcs.aspx

Steps to reproduce are:

1. Click on "add new record" command
2. Click on delete button, the one that is a red "X"
3. Click on Save Changes button.
4. It throws an JS error that is visible on any browser dev tools, attached is a screenshot showing that error.

Please fix it soon.
Thanks.