Looks like that error comes from when you have Footprint in SelectionShape in VisualActor, but then don't have a separate Footprint element. We only use that with field and flora, and actually flora doesn't have Footprint but the things that inherit it (bush, tree) do. (Changed in rP20345 (probably shouldn't have been, my mistake).) So my guess would be that you have something that has parent = template_gaia_flora but doesn't have a Footprint set.