Structure: Item returned no child

In most cases, you will want to return a child when a list item is clicked. If you are receiving this warning, your list has probably not defined a child/child resolver, or the child resolver is returning undefined.

You usually want to specify a child for an item:

S.listItem()
  .title('George R. R. Martin')
  .child(
    S.documentList()
      .title('GRRM books')
      .filter('_type == "book" && author._ref == "grrm"')
  )

Omitting .child(...) still logs Pane returned no child. There is no supported way to mark an item as an intentional leaf.