error "Failed to process setAttr o is undefined (TypeError)"

	<tabbox vflex="1" id="miTab">
		<tabs>
			<tab label="1" id="1"></tab>
			<tab label="1" id="2"></tab>
			... more tabs ...
		</tabs>
		<tabpanels vflex="1">
			<tabpanel id="tb1" >
				<tree id="myTree1"  vflex="1" hflex="1" sclass="myclass" >
					<treecols sizable="true">
				        <treecol label="1"  id="c1" sortAscending="${des_asc}" sortDescending="${des_dsc}" hflex="2"></treecol>
				        <treecol label="2" 	id="c2" sortAscending="${cod_asc}" sortDescending="${cod_dsc}" visible="false" ></treecol>
						... more cols ...
					<treechildren>
			                </treechildren>
				</tree>
			</tabpanel>
			<tabpanel id="tb2">
				<tree id="myTree2" vflex="1" hflex="1">
					<treecols sizable="true">
				        <treecol label="A" 	id="cA" sortAscending="${des_asc}" sortDescending="${des_dsc}"  hflex="2"></treecol>
				        <treecol label="B" 	id="cB" sortAscending="${cod_asc}" sortDescending="${cod_dsc}" visible="false"  hflex="1" ></treecol>
						... more cols ...
					<treechildren>
  			                </treechildren>
				</tree>
			</tabpanel>
			... more tabpanels ...

	public void render(Treeitem treeItem, Object data, int arg2) throws Exception {

		DefaultTreeNode treeNode = (DefaultTreeNode) data;
		treeItem.setValue(treeNode);
		Treerow tr;
		if (treeItem.getTreerow() == null) {
			tr = new Treerow();
			tr.setParent(treeItem);
		} else {
			tr = treeItem.getTreerow();
			tr.getChildren().clear();
		}

		MyRowInfo row = (MyRowInfo)treeNode.getData();

		Treecell desc=new Treecell();
		desc.appendChild(new Label(mytext));
		if (mycondition) {
			desc.setClass("myclass");
		}
		tr.appendChild(desc);

		Treecell cell2=new Treecell();
		Div mydiv=new Div();
		mydiv.appendChild(new Label(myothertext));
		if (somecondition) {
			mydiv.setClass("oneclass");
		} else if (somecondition) {
			mydiv.setClass("otherclass");
		} else {
			mydiv.setClass("thirdclass");
		}
		cell2.appendChild(mydiv);
		tr.appendChild(cell2);
			
		... more cells ...

		if (!treeItem.isListenerAvailable(Events.ON_OPEN, true)) { 
			treeItem.addEventListener(1000,Events.ON_DOUBLE_CLICK, new EventListener() { 
				public void onEvent(Event event) throws Exception {
					Treeitem ti=(Treeitem)event.getTarget();
					ti.setSelected(true);
					DefaultTreeNode dtn=(DefaultTreeNode)ti.getValue();
					MyRowInfo row = (MyRowInfo)dtn.getData();
					row.changeOpen();
					ti.setOpen(row.isOpen());
				}
			}); 			
			treeItem.addEventListener(1000,Events.ON_OPEN, new EventListener() { 
				public void onEvent(Event event) throws Exception {
					Treeitem ti=(Treeitem)event.getTarget();
					ti.setSelected(true);
					DefaultTreeNode dtn=(DefaultTreeNode)ti.getValue();
					MyRowInfo row = (MyRowInfo)dtn.getData();
					row.setOpen(((OpenEvent)event).isOpen());
				}
			}); 			
			treeItem.addEventListener(1000,Events.ON_RIGHT_CLICK, new EventListener() { 
				public void onEvent(Event event) throws Exception {
					((Treeitem)event.getTarget()).setSelected(true);
				}
			});
		}
		
		if (tr.getContext()==null) {
			Menupopup popup=new Menupopup();
			popup.setPage(treeItem.getPage());
			popup.setWidth("300px");

			if (somecondition) {
				Menuitem mnc=new Menuitem("sometext");
				mnc.setImage("/images/image.gif");
				mnc.setStyle("background-repeat:none");
				ComponentsCtrl.applyForward(mnc, "somepoint.onClick");
				popup.appendChild(mnc);
				...more menuitems ...
			}
			tr.setContext(popup);
		}

		treeItem.setOpen(row.isOpen()); 
		DefaultTreeModel model = (DefaultTreeModel) treeItem.getTree().getModel();
		if (row.isOpen())
			model.addOpenObject(data);		
	}