Bug fixed.

joram/joram/mom/core/src/main/java/org/objectweb/joram/mom/util/MessageIdListImpl.java

@@ -142,6 +142,11 @@ public class MessageIdListImpl implements MessageIdList, Encodable,
     }
   }
   
+  @Override
+  public String toString() {
+    return "MessageIdListImpl [listId=" + listId + ", list=" + list + "]";
+  }
+
   public static class MessageIdListImplEncodableFactory implements EncodableFactory {
 
     public Encodable createEncodable() {

joram/joram/mom/core/src/main/java/org/objectweb/joram/mom/util/MessageIdListImplFactory.java

@@ -36,7 +36,9 @@ public class MessageIdListImplFactory extends MessageIdListFactory {
   public MessageIdList loadMessageIdList(String listId) throws Exception {
     // TODO: as we know the type, the method 'loadByteArray' would be more efficient
     MessageIdListImpl res = (MessageIdListImpl) AgentServer.getTransaction().load(listId);
-    res.setListId(listId);
+    if (res != null) {
+      res.setListId(listId);
+    }
     return res;
   }