message: Fix error in iterator size
diff: @@ -421,7 +421,7 @@ class filter_iterator : public std::iterator<
  if (this->size_c_ > 0) {
  return this->size_c_;
  }
  - filter_iterator it = *this;
  + filter_iterator it = this->begin();
  size_t size = 0;
  while (it++ != std::end(it)) size++;
  