message: simplified FilterCollector#for_segment
diff: @@ -107,17 +107,14 @@ where
  field_name
  ))
  })?;
  - let child_segment_collector = self.collector.for_segment(segment_local_id, segment_reader);
  - match child_segment_collector {
  - Ok(segment_collector) => Ok(FilterSegmentCollector::<TSegmentCollector> {
  + let segment_collector = self
  + .collector
  + .for_segment(segment_local_id, segment_reader)?;
  + Ok(FilterSegmentCollector::<TSegmentCollector> {
  fast_field_reader,
  segment_collector: segment_collector,
  predicate: self.predicate,
  - }),
  - Err(_) => Err(TantivyError::SystemError(
  - "Could not open segment: ".to_owned(),
  - )),
  - }
  + })
  }
  fn requires_scoring(&self) -> bool {
  