code: public static <R, E extends Exception> Nullable<R> ifOrEmpty(final boolean b, final Try.Supplier<R, E> supplier) throws E {
          if (b) {
              return Nullable.of(supplier.get());
          } else {
              return Nullable.empty();
          }
      }
docs: Returns a {@code Nullable} with value got from the specified {@code supplier} if {@code b} is {@code true},
  otherwise returns an empty {@code Nullable} if {@code b} is false.
  
  @param b
  @param supplier
  @return
  @throws E