code: @Override
      protected boolean isButtonEnabledForHistoryReference(HistoryReference historyReference) {
          final SiteNode siteNode = getSiteNode(historyReference);
          if (siteNode != null && !isButtonEnabledForSiteNode(siteNode)) {
              return false;
          }
          return true;
      }
docs: Tells whether or not the button should be enabled for the given selected message.
  <p>
  Calls the method {@code isButtonEnabledForSiteNode(SitNode)} passing as parameter the site node extracted from the given
  {@code historyReference}.
  
  @param historyReference the selected message, never {@code null}
  @return {@code true} if the button should be enabled for the given selected message, {@code false} otherwise.