修改service bug

swiftCore/src/main/java/com/brilliance/swift/mx2mt/Mx2MtCreatorManager.java

@@ -43,6 +43,9 @@ public class Mx2MtCreatorManager {
                     .trim();
             Mx2MtContext context = new Mx2MtContext();
             String service = getServiceMessage(xml);
+            if(StringUtil.isEmpty(service)){
+                service = "";
+            }
             context.set(Mx2MtContextIdentifier.MX_TO_MT_SERVICE,service);
             Document document = DocumentHelper.parseText(xml);
             context.set(Mx2MtContextIdentifier.MX_TO_MT_LISTENER_CLASS, new Mx2MtListener()); //注册监听器