dropChildRenderObject method
Drop child from this element's render object. childElement is null
when the drop happens as part of a re-sync pass rather than an element
removal.
Implementation
@override
void dropChildRenderObject(RenderObject child, Element? childElement) {
final renderFlex = renderObject as RenderFlex?;
if (renderFlex == null) return;
if (child is! RenderBox || child.parent != renderFlex) return;
renderFlex.remove(child);
}