On saving <UML:Operation> avoid empty <UML:BehavioralFeature.parameter/>

umbrello/uml1model/operation.cpp
- In function saveToXMI1, before calling writer.writeStartElement for
  "UML:BehavioralFeature.parameter", if m_pSecondary is null and m_List
  is empty then write </UML:Operation> closing element and return.

CCBUG: 363582