[bugfix] Lazy components empty content handling

[girouxc]

This small change makes it easier to manage the case where there are empty items in the LazyColumn or LazyRow.

When a child is removed from the rendering tree, it messes up with the indexing, resulting in cases where navigating down will not load new children.

This MR fixes it by making the decision to increase the offset consider the actual number of children rendered.

Thanks !