[OPEN EXTJSIV-1223] [B3] examples\grid\groupgrid.html refuse to use virtual scrolling
Virtual scrolling is the lazy rendering, avoiding creation of DOM element when rows are not visible. It's needed on any grid having more than 250 rows.
There is an example of virtual scrolling under \examples\grid\buffer-grid.html.
I activate virtual scrolling for examples\grid\groupgrid.html but then the scroller doesn't scroll anything anymore.
The way I activate it is with this: