If a user tries to call renderer.remove() after the Renderable has already been removed the remove method will generate an NPE:

ava.lang.NullPointerException
        at
com.icesoft.faces.async.render.GroupAsyncRenderer.remove(GroupAsyncRenderer.java:127)
        at
com.efunds.oe.fm.pb.AbstractRenderableBean.removePolling(AbstractRenderableBean.java:117)
        at
com.efunds.oe.fm.pb.AbstractRenderableBean.viewDisposed(AbstractRenderableBean.java:210)
        at com.icesoft.faces.context.View.notifyViewDisposal(View.java:221)
        at com.icesoft.faces.context.View.dispose(View.java:191)
...

suggested fix:

public void remove(Renderable renderable) {
   if( group != null ){
synchronized (group) {
            Iterator iter = group.iterator();
            while (iter.hasNext()) {
                WeakReference ref = (WeakReference) iter.next();
                if (renderable == (Renderable) ref.get()) {
                    group.remove(ref);
                    if (log.isTraceEnabled()) {
                        log.trace(name + " removing " + renderable);
                    }
                    return;
                }
            }
            if (log.isWarnEnabled()) {
                log.warn(name + " does not contain " + renderable);
            }
        }
      }
    }