code: protected User safeGetSender(MessageEnvelope envelope) {
  		if (envelope != null && envelope.getSender() != null
  				&& envelope.getSender().getId() != null) {
  			return envelope.getSender();
  		}
  		return new User();
  	}
docs: Retrieves the sender from an envelope. It never returns null.
  
  @param envelope
  the message envelope.
  @return a {@link User} containing the sender if found, empty otherwise.
  It never returns null.