code: @SuppressFBWarnings(value = "NP_BOOLEAN_RETURN_NULL", justification = "That's the point (but dubious)")
      public static Boolean falseToNull(Boolean bool) {
          if (bool != null && bool) {
              return true;
          }
          return null;
      }
docs: If bool is false change it to null, otherwise do nothing.
  
  @param bool boolean
  @return true if bool is true, null otherwise