I am battling an intermittent error. According to EurekaLog, the error occurs in this routine:

I am battling an intermittent error. According to EurekaLog, the error occurs in this routine:

procedure TTreeItem.Clear;
var
  j: integer;
  LinkedItem: TLinkedItem;
begin
  for j:=0 to LeafSize-1 do begin
    if Items[j] <> nil then begin
      if Items[j] is TTreeItem then begin <---- exception thrown here
        TTreeItem(Items[j]).Free;
        Items[j] := Nil;
      end
      else begin
        LinkedItem:=TLinkedItem(Items[j]);
        while LinkedItem <> nil do begin
          Owner.DestroyItem(LinkedItem.Value);
          LinkedItem:=LinkedItem.Next;
        end;
        TLinkedItem(Items[j]).Free;
        Items[j] := Nil;
      end;
    end;
  end;
end;

The code seems all too simple. Items added are TTreeItems, so the test for whether the item is a TTreeItem is almost redundant, but the question is, how can an is test on the item throw an exception?

The code is taken from a Hash Trie implementation which is used in a third-party component, a version which is no longer supported. 

I do not have the option of installing a current version of the component, and the problem, though intermittent, happens relatively often.

Update: We will be moving away from this component for new work, but at present (and in D2007) we must find a way to make this work.

This one is driving me crazy, which is why I am posting at 4:00 in the morning: I woke up trying to imagine solutions....