message: Deallocate value region in case of empty key
diff: @@ -157,10 +157,10 @@ impl Iterator for ExternalIterator {
  }
  let key = unsafe { consume_region(key_ptr).unwrap() };
  + let value = unsafe { consume_region(value_ptr).unwrap() };
  if key.is_empty() {
  return None;
  }
  - let value = unsafe { consume_region(value_ptr).unwrap() };
  Some((key, value))
  }
  }
  