docs: public List<String> getValueList(List<String> defaultValue) {
  
          if (this == CmsProperty.NULL_PROPERTY) {
              // return the default value if this property is the null property
              return defaultValue;
          }
  
          // somebody might have set both values to null manually
          // on a property object different from the null property...
          return (m_structureValue != null)
          ? getStructureValueList()
          : ((m_resourceValue != null) ? getResourceValueList() : defaultValue);
      }