api: dont write back empty header (#966)

pkg/api/chunk.go

@@ -130,6 +130,8 @@ func (s *server) chunkGetHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	w.Header().Set("Content-Type", "binary/octet-stream")
-	w.Header().Set(TargetsRecoveryHeader, targets)
+	if targets != "" {
+		w.Header().Set(TargetsRecoveryHeader, targets)
+	}
 	_, _ = io.Copy(w, bytes.NewReader(chunk.Data()))
 }

pkg/api/file.go

@@ -353,7 +353,9 @@ func (s *server) downloadHandler(w http.ResponseWriter, r *http.Request, referen
 	w.Header().Set("ETag", fmt.Sprintf("%q", reference))
 	w.Header().Set("Content-Length", fmt.Sprintf("%d", l))
 	w.Header().Set("Decompressed-Content-Length", fmt.Sprintf("%d", l))
-	w.Header().Set(TargetsRecoveryHeader, targets)
+	if targets != "" {
+		w.Header().Set(TargetsRecoveryHeader, targets)
+	}
 
 	http.ServeContent(w, r, "", time.Now(), langos.NewBufferedLangos(reader, lookaheadBufferSize(l)))
 }