Crash when importing DOM level 1 into SOAP Message

[jmongard]

In saaj-impl version 1.5.x, When trying to import an element created with Document::createElement into a SOAP message it crashes with the exception:
java.lang.IllegalArgumentException: local part cannot be "null" when creating a QName

This type of import worked fine in java 8 / saaj-impl 1.3.

public void testImportNodeIntoMessage() throws Exception {
    DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
    dbf.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, true);
    dbf.setNamespaceAware(true);
    DocumentBuilder db = dbf.newDocumentBuilder();
    Document doc = db.newDocument();
   
    Element request = doc.createElementNS("http://example.com/", "request");
    
    //Adding a DOM level 1 element causes exception when importing
    request.appendChild(doc.createElement("DOMLevel1"));
    
    SOAPMessage msg = MessageFactoryImpl.newInstance().createMessage();        
	Node importNode = msg.getSOAPPart().importNode(request, true);		
	assertNotNull(msg.getSOAPBody().appendChild(importNode));   
}