code: protected String classifyIfEmpty(final String group, final String message) {
          String category = StringUtils.capitalize(group);
          if (StringUtils.isEmpty(category)) {
              category = classifyWarning(message);
          }
          return category;
      }
docs: Returns a category for the current warning. If the provided category is
  not empty, then a capitalized string is returned. Otherwise the category
  is obtained from the specified message text.
  @param group
  the warning category (might be empty)
  @param message
  the warning message
  
  @return the actual category