code: protected String safeGetSenderId(MessageEnvelope envelope) {
  		if (envelope != null && envelope.getSender() != null
  				&& envelope.getSender().getId() != null) {
  			return envelope.getSender().getId();
  		}
  		return "";
  	}
docs: Retrieves the sender ID from an envelope. It never returns null.
  
  @param envelope
  the message envelope.
  @return the sender ID if found or an empty String otherwise. It never
  returns null.