Adding a new item to Grid's DataProvider and using scrollToIndex to the end, shows empty rows in the top.

[johannest]

Vaadin 14.1.17, Chome (Win 10).

Issue description: When having a Grid with empty space in the bottom (row count less than grid's size). And, adding a new item(s) to backing (list) dataprovider, and using scrollToIndex to scroll to the end. Then, for each item, an empty row is shown in the top of the Grid like in the screenshot below:

Code example to reproduce the issue:

@Route("scrollTo")
@Theme(Lumo.class)
public class GridScrollToTest extends VerticalLayout {

    private Grid<Dto> grid = null;
    private ListDataProvider<Dto> dataProvider;

    public GridScrollToTest() {
        setSizeFull();
        Button addItem = new Button("Add");
        addItem.addClickListener(buttonClickEvent -> {
            dataProvider.getItems().add(getNewMockDto());
            dataProvider.refreshAll();
            grid.scrollToIndex(dataProvider.getItems().size());
        });

        grid = new Grid<>(Dto.class);
        List<Dto> data = new ArrayList<>();
        for (int i = 0; i < 10; i++) {
            data.add(getNewMockDto());
        }
        dataProvider = new ListDataProvider<>(data);
        grid.setDataProvider(dataProvider);

        add(addItem, grid);
    }

    private Dto getNewMockDto() {
        return new Dto(UUID.randomUUID().toString());
    }

    public static class Dto {
        private String uuid;

        public Dto(String uuid) {
            super();
            this.uuid = uuid;
        }

        public String getUuid() {
            return uuid;
        }
    }
}

[johannest]

Workaround: https://gist.github.com/johannest/1dd2faa2570935afe6ba175747741abd

[Frettman]

scrollToEnd seems to have the exact same issue. And it's not just additional empty space at the top: when this happends it seems to remove/replace my top most item. This seems to be triggered when adding an item makes scrolling necessary.

[mvysny]

@yuriy-fix Hello, will this be back-ported to Vaadin 14.x?