title: Null pointer exception in oracle-jdbc database change notification
body: <pre><code>DCNDemoListener: got an event (com.datasync.DCNDemoListener@587bf0 running on thread Thread[Thread-2,5,main])
  Exception in thread "Thread-2" java.lang.NullPointerException
      at com.datasync.DCNDemoListener.onDatabaseChangeNotification(DBChangeNotification.java:142)
      at oracle.jdbc.driver.NTFRegistration.notify(NTFRegistration.java:191)
      at oracle.jdbc.driver.NTFConnection.unmarshalNSDataPacket(NTFConnection.java:578)
      at oracle.jdbc.driver.NTFConnection.unmarshalOneNSPacket(NTFConnection.java:404)
      at oracle.jdbc.driver.NTFConnection.run(NTFConnection.java:181)
  </code></pre>
  
  <p>Here is my code:</p>
  
  <pre><code>public void onDatabaseChangeNotification(DatabaseChangeEvent e)
        {
          Thread t = Thread.currentThread();
          System.out.println("DCNDemoListener: got an event ("+this+" running on thread "+t+")");
          System.out.println(e.getTableChangeDescription()[0].getRowChangeDescription()[0].getRowid().stringValue()); // line142
          System.out.println(e.toString());
          synchronized( demo )
          { demo.notify();}
        }
  </code></pre>
  
  <p>Tring to figure out but I have no clue what went wrong :(</p>