skips compact if store is stopping

weed/storage/store_vacuum.go

@@ -26,6 +26,9 @@ func (s *Store) CompactVolume(vid needle.VolumeId, preallocate int64, compaction
 	return fmt.Errorf("volume id %d is not found during compact", vid)
 }
 func (s *Store) CommitCompactVolume(vid needle.VolumeId) (bool, error) {
+	if s.isStopping {
+		return false, fmt.Errorf("volume id %d skips compact because volume is stopping", vid)
+	}
 	if v := s.findVolume(vid); v != nil {
 		return v.IsReadOnly(), v.CommitCompact()
 	}