Error updating subsequent component about searchable_dropdown HOT 5 OPEN

updateSelectedItems({dynamic sel = const NotGiven()}) {
    List<int> updatedSelectedItems;
    if (widget.multipleSelection) {
      if (!(sel is NotGiven)) {
        updatedSelectedItems = sel as List<int>;
      } else {
        updatedSelectedItems =
            List<int>.from(widget.selectedItems ?? List<int>());
      }
    } else {
      T val = !(sel is NotGiven) ? sel as T : widget.value;
      if (val != null) {
        int i = indexFromValue(val);
        if (i != null && i != -1) {
          updatedSelectedItems = [i];
        }
      } else {
        updatedSelectedItems = null;
      }
      if (updatedSelectedItems == null) updatedSelectedItems = List<int>();
    }
    if (!widget.multipleSelection) {
      selectedItems.retainWhere((element) =>
          updatedSelectedItems.any((selected) => selected == element));
    }
    updatedSelectedItems.forEach((selected) {
      if (!selectedItems.any((element) => selected == element)) {
        selectedItems.add(selected);
      }
    });
  }

  @override
  void initState() {
    if (widget.multipleSelection) {
      selectedItems = List<int>.from(widget.selectedItems ?? []);
    } else if (widget.value != null) {
      int i = indexFromValue(widget.value);
      if (i != null && i != -1) {
        selectedItems = [i];
      }
    }
    if (selectedItems == null) selectedItems = [];
    updateSelectedItems();
    super.initState();
  }

  @override
  void didUpdateWidget(SearchableDropdown oldWidget) {
    super.didUpdateWidget(oldWidget);
    updateSelectedItems();
  }

if (!widget.multipleSelection) {
      selectedItems.retainWhere((element) =>
          updatedSelectedItems.any((selected) => selected == element));
    }