/**
* @return Top Node Container available in the Application Window. Null, if
* the Top Window is not a Node Container
*/
private NodeContainer getTopNodeContainer() {
Window window = getTopWindow();
NodeContainer nodeContainer = null;
if (window != null) {
WorldObject wo = window.getContents();
if (wo instanceof NodeContainer) {
nodeContainer = (NodeContainer) wo;
}
} else {
nodeContainer = this;