code: private String getEmptyMessage() {
  
          switch (m_mode) {
              case sources:
                  return org.opencms.gwt.client.Messages.get().key(org.opencms.gwt.client.Messages.GUI_USAGE_EMPTY_0);
              case targets:
              default:
                  return org.opencms.gwt.client.Messages.get().key(org.opencms.gwt.client.Messages.GUI_TARGETS_EMPTY_0);
          }
  
      }
docs: Gets the message to use for an empty relation list.<p>
  
  @return the message to display for an empty relation list