Circle in tree connectors - how to get rid of it ? (BUG?)

[Remyx]

I am using a tree with all nodes looking like folders (no leaves) (something like explorer).
The problem is, in a particular configuration a circle sign appears instead of a connector.

How can I remove the little ugly circle displayed before Item2 ?

Thanks in advance,

Remi

the code to reproduce this

public class MainModule implements EntryPoint {

    public void onModuleLoad() {
        Canvas canvas = new Canvas();
        canvas.draw();

        final IButton stretchButton = new IButton("SHOW TREE");
        stretchButton.setWidth(150);
        stretchButton.setShowRollOver(true);
        stretchButton.setShowDisabled(true);
        stretchButton.setShowDown(true);       
            stretchButton.addClickHandler(new ClickHandler() {
            public void onClick(com.smartgwt.client.widgets.events.ClickEvent event) {        
                final Window winModal = new Window();
                winModal.setWidth(360);
                winModal.setHeight(600);
                winModal.setTitle("Modal Window");
                winModal.setShowMinimizeButton(false);
                winModal.setIsModal(true);
                winModal.setShowModalMask(true);
                winModal.centerInPage();

                DynamicForm form = new DynamicForm();
                form.setHeight100();
                form.setWidth100();
                form.setPadding(5);
                form.setLayoutAlign(VerticalAlignment.BOTTOM);
                TextItem textItem = new TextItem();
                textItem.setTitle("Text");
                DateItem dateItem = new DateItem();
                dateItem.setTitle("Date");
                DateItem dateItem2 = new DateItem();
                dateItem2.setTitle("Date");
                dateItem2.setUseTextField(true);
                form.setFields(textItem, dateItem, dateItem2);


                Tree tree = new Tree();
                TreeNode[] treeNodes = new TreeNode[4];
                treeNodes[0] = new TreeNode();
                treeNodes[0].setID("0");
                treeNodes[0].setTitle("root");
                treeNodes[0].setIsFolder(true);

                treeNodes[1] = new TreeNode();
                treeNodes[1].setTitle("item1");
                treeNodes[1].setID("1");
                treeNodes[1].setParentID("0");
                treeNodes[1].setIsFolder(true);

                treeNodes[2] = new TreeNode();
                treeNodes[2].setTitle("item2");
                treeNodes[2].setID("2");
                treeNodes[2].setParentID("0");
                treeNodes[2].setIsFolder(true);
                //add empty children array to avoid displaying plus sign (+) if there are no sub-leaves
                TreeNode[] emptyChildrenArray = new TreeNode[]{};
                treeNodes[2].setChildren(emptyChildrenArray);

                treeNodes[3] = new TreeNode();
                treeNodes[3].setTitle("item11");
                treeNodes[3].setID("3");
                treeNodes[3].setParentID("1");
                treeNodes[3].setIsFolder(true);
                //add empty children array to avoid displaying plus sign (+) if there are no sub-leaves
                TreeNode[] emptyChildrenArray2 = new TreeNode[]{};
                treeNodes[3].setChildren(emptyChildrenArray2);

                tree.setModelType(TreeModelType.PARENT);
                //tree.setIdField("folderId");
                //tree.setParentIdField("parentFolderId");
                tree.setNameProperty("displayName");
                tree.setRootValue("1");
                tree.setData(treeNodes);


                TreeGrid folderTreeGrid = new TreeGrid();
                folderTreeGrid.setWidth(360);
                folderTreeGrid.setHeight(300);

                folderTreeGrid.setData(tree);
                folderTreeGrid.setShowConnectors(true);
                folderTreeGrid.setShowFullConnectors(false);
                folderTreeGrid.setExpansionMode(ExpansionMode.DETAIL_FIELD);
                folderTreeGrid.setPreventDuplicates(false);

                form.addChild(folderTreeGrid);

                winModal.addItem(form);
                winModal.show();
            }


        });
        canvas.addChild(stretchButton);
    }
}

SmartGWT 2.2