tree items cause JS error with radiogroup

Steps to Reproduce

run the attachment radiogroup-rerender-simplified.zul

click in the following sequence
1. "refresh tree"
2. "rerender radio group"
3. "refresh tree"
4. "rerender radio group"

Current Result

after 2nd time refreshing the tree, it is no longer possible to re-render the radio group resulting in a JS error:

zk.wpd:35294 Uncaught TypeError: group.getName is not a function
    at init.getName (zk.wpd:35294)
    at init.contentAttrs_ (zk.wpd:34178)
    at init.radio$mold$ (zk.wpd:35351)
    at init.redraw (zk.wpd:20252)
    at init.radiogroup$mold$ (zk.wpd:35613)
    at init.redraw (zk.wpd:20252)
    at init.redrawHTML_ (zk.wpd:20630)
    at init.insertChildHTML_ (zk.wpd:20740)
    at init.appendChild (zk.wpd:19468)
    at Array.fn (zk.wpd:27091)

Expected Result

re-rendering the radio group

Debug Info

this only happens when "org.zkoss.zul.client.rod" is enabled for the tree
this still worked in 8.5.0

Root Cause

when debugging through the JS code the radio._group refers to a Treeitem-widget instead of a Radiogroup

Workaround

disable client-rod for the tree

	<tree id="tree" model="${treeModel}">
		<custom-attributes org.zkoss.zul.client.rod="false"/>
	</tree>