title: Prefix is null when using client stubs
body: <p>I had to use axis to generate stubs because the SOAP I am working with uses RPC. After setting up the code to post I am receiving the below stack trace. If anyone has had this issue please help. From using the debug tool in Eclipse I can see that Axis is using default prefixes, but the issue is that one of the prefixes it uses has already been used so it returns null. Does anyone know why this may be happening?</p>
  
  <pre><code>AxisFault
   faultCode: {http://schemas.xmlsoap.org/soap/envelope/}Server.userException
   faultSubcode: 
   faultString: java.io.IOException: java.io.IOException: Non nillable element 'prefix' is null.
   faultActor: 
   faultNode: 
   faultDetail: 
      {http://xml.apache.org/axis/}stackTrace:java.io.IOException: java.io.IOException: Non nillable element 'prefix' is null.
      at org.apache.axis.encoding.ser.BeanSerializer.serialize(BeanSerializer.java:275)
      at org.apache.axis.encoding.SerializationContext.serializeActual(SerializationContext.java:1504)
      at org.apache.axis.encoding.SerializationContext.serialize(SerializationContext.java:980)
      at org.apache.axis.encoding.SerializationContext.outputMultiRefs(SerializationContext.java:1055)
      at org.apache.axis.message.SOAPBody.outputImpl(SOAPBody.java:145)
      at org.apache.axis.message.SOAPEnvelope.outputImpl(SOAPEnvelope.java:478)
      at org.apache.axis.message.MessageElement.output(MessageElement.java:1208)
      at org.apache.axis.client.Call.invoke(Call.java:2757)
      at org.apache.axis.client.Call.invoke(Call.java:2443)
      at org.apache.axis.client.Call.invoke(Call.java:2366)
      at org.apache.axis.client.Call.invoke(Call.java:1812)
  </code></pre>