docs: private FastRequestHandler verifyBase(URL baseUrl, String baseSupplied) {
          if (null == baseUrl) {
              if ("META-INF/resources/webjars".equalsIgnoreCase(baseSupplied)) {
                  // webjars not provided, just ignore it.
              } else {
                  logger.warn("URL base not exists: " + baseSupplied);
              }
              return AlwaysNotFound.INSTANCE;
          }
          return null;
      }