private boolean isValidNavigation(ITreeNode node, boolean unread) {
Object data = node.getData();
/* Check for Unread news if required */
if (data instanceof INewsMark) {
INewsMark newsmark = (INewsMark) data;
if (unread && newsmark.getNewsCount(EnumSet.of(INews.State.NEW, INews.State.UNREAD, INews.State.UPDATED)) == 0)
return false;
}
/* Folders and Entity Groups are no valid navigation nodes */
else if (data instanceof IFolder || data instanceof EntityGroup)