code: public String getPreselectOption(String siteRoot, List<CmsSiteSelectorOption> options) {
  
          if ((siteRoot == null) || options.isEmpty()) {
              return null;
          }
          for (CmsSiteSelectorOption option : options) {
              if (CmsStringUtil.joinPaths(siteRoot, "/").equals(CmsStringUtil.joinPaths(option.getSiteRoot(), "/"))) {
                  return option.getSiteRoot();
              }
          }
          return options.get(0).getSiteRoot();
      }
docs: Gets the option which should be preselected for the site selector, or null.<p>
  
  @param siteRoot the site root
  @param options the list of options
  
  @return the key for the option to preselect