static IntRange tok_findNextEmptyLineWhitespace(S s, int i) {
  char c;
  int k = i, l = l(s);
  
  while (k < l) {
    int j = k, breaks = 0;
    while (j < l && isSpace(c = s.charAt(j))) {
      ++j;
      if (c == '\n') ++breaks;
    }
    if (breaks >= 2) ret intRange(k, j);
    while (j < l && !isSpace(s.charAt(j))) ++j;
    k = j;
  }
  
  null;
}