docs: private void saveWindowSize(Dimension size) {
  		if (size != null) {
  			if (getExtendedState() == Frame.NORMAL) {
  				if (logger.isDebugEnabled()) logger.debug("Saving preference " + PREF_WINDOW_SIZE + "=" + size.width + "," + size.height);
  				this.preferences.put(prefnzPrefix+PREF_WINDOW_SIZE, size.width + ","	+ size.height);
  			} else {
  				if (logger.isDebugEnabled()) logger.debug("Preference " + PREF_WINDOW_SIZE + " not saved, cause window state is not 'normal'.");
  			}
  		}
  	}