jQuery Grid Plugin - jqGrid

I have a grid with grouping on one column. Data are loaded from a server using json. All works fine if data fits in the first page. All other pages are empty.

I found a possible bug in groupingRender @11783. This code loops on grdata to build the HTML string to output

 for(kk=sgr;kk<end;kk++) {
    if(!grdata[kk - offset]) { break; }
    str += grdata[kk - offset].join('');
 }

With a pagesize = 20, on page 2, sgr and end are also 20. Looking at how th kk index is used i think the for test should be kk < end + offset. Code now is

for(kk=sgr;kk<end+offset;kk++) {
 if(!grdata[kk - offset]) { break; }
 str += grdata[kk - offset].join('');
}

This fixed things for me. I would like a confirm that this is a bug, else I should find what trigger this in the application.

Thanks