Group paging does not work correctly with virtualization and one level of grouping

[ag-petrov]

Bug report

When there is a single level of grouping and virtualization is enabled the when expanding the first group and scrolling down the next request repeats the first one and fetches the same data. More information alongside with a sample can be found in ticket - 1527383

Reproduction of the problem

Run this dojo, expand Argentina and start scrolling down till a request is made.

Current behavior

The request duplicates the already existing data

Expected/desired behavior

The next set of data should be fetched