docs: public static <T> List<T> addAllNotNull(List<T> to, List<? extends T> what) {
          List<T> data = safeList(to);
          if (!isEmpty(what)) {
              for (T t : what) {
                  if (t != null) {
                      data.add(t);
                  }
              }
          }
          return data;
      }