empty deleted file

go/storage/volume.go

@@ -232,6 +232,7 @@ func (v *Volume) delete(n *Needle) (uint32, error) {
 		if _, err = v.dataFile.Seek(int64(nv.Offset*NeedlePaddingSize), 0); err != nil {
 			return nv.Size, err
 		}
+		n.Data = make([]byte,0)
 		_, err = n.Append(v.dataFile, v.Version())
 		return nv.Size, err
 	}