             }
         )
         lotStandingsView.tag = ViewTags.lotStandings.rawValue
-        headerStack.addSubview(lotStandingsView, withTopMargin: "0", sideMargin: "0")
+        headerStack?.addSubview(lotStandingsView, withTopMargin: "0", sideMargin: "0")
     }
 
     var isCompactSize: Bool { return traitCollection.horizontalSizeClass == .compact }


        // TODO: Recreate everything from scratch when size class changes.

        headerStack = ORTagBasedAutoStackView()
        saleArtworksViewController = ARModelInfiniteScrollViewController()

        ar_addAlignedModernChildViewController(saleArtworksViewController)

        self.networkModel.fetchLotStanding().next { [weak self] lotStandings in
            saleViewModel.updateLotStandings(lotStandings)

            if let existingLotStandingsView = self?.headerStack?.viewWithTag(ViewTags.lotStandings.rawValue) {
                self?.headerStack?.removeSubview(existingLotStandingsView)
            }

            self?.addLotStandings()
