code: public AttributeCriterion getSearchCriterion() {
  		Object operator = operatorSelect.getValue();
  		if (operator != null) {
  			return AttributeCriterionUtil.getSearchCriterion(layer.getServerLayerId(), selectedAttribute, valueItem,
  					org.geomajas.gwt.client.widget.attribute.AttributeCriterionPane.
  							getOperatorCodeFromLabel(operator.toString()));
  		}
  		return null;
  	}
docs: Return the actual search criterion object, or null if not all fields have been properly filled.
  
  @return search criterion