gmap2, wicket 6.9 and ajax refresh

Since I've upgrade from wicket 6.8.0 to wicket 6.9.1, many of my gmap panel
are not working anymore when I do an ajax refresh on them.

From what's I've discovered is that on the refresh the
Wicket.Event.add(window, "onUnload", function(event) {
google.maps.Unload();;});
has became
(function(){google.maps.Unload();})

That is not good!

The code in gmap2 has not changed.
It use : response.render(OnEventHeaderItem.forScript("window", "onUnload",
"google.maps.Unload();"));
that produce :
@Override
public void render(Response response)

JavaScriptUtils.writeJavaScript(response, "Wicket.Event.add(" +
getTarget() + ", \"" +
getEvent() + "\", function(event) { " + getJavaScript() + ";});");

In wicket 6.8 when I refresh the map, the program does go in the render
function, but not in wicket 6.9.
That is very strange...

*I think it has something to do with :
https://issues.apache.org/jira/browse/WICKET-5234*

You can reproduce it using gmap2-exmaple in the "listener" page.
Just click on the "true/false" button and then the map get stuck!