code: private void _handleEmptyValue(TypedValueDecoder dec)
          throws XMLStreamException
      {
          try { // default action is to throw an exception
              dec.handleEmptyValue();
          } catch (IllegalArgumentException iae) {
              throw _constructTypeException(iae, "");
          }
      }
docs: Method called to handle value that has empty String
  as representation. This will usually either lead to an
  exception, or parsing to the default value for the
  type in question (null for nullable types and so on).