[#1492] metabase: Ensure Unmarshal() is called on a cloned slice

The slice returned from bucket.Get() is only valid during the tx
lifetime. Cloning it is not necessary everywhere, but better safe than
sorry.

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

pkg/local_object_storage/metabase/exists.go

@@ -1,6 +1,7 @@
 package meta
 
 import (
+	"bytes"
 	"context"
 	"fmt"
 	"time"
@@ -215,7 +216,7 @@ func getSplitInfo(tx *bbolt.Tx, cnr cid.ID, key []byte) (*objectSDK.SplitInfo, e
 
 	splitInfo := objectSDK.NewSplitInfo()
 
-	err := splitInfo.Unmarshal(rawSplitInfo)
+	err := splitInfo.Unmarshal(bytes.Clone(rawSplitInfo))
 	if err != nil {
 		return nil, fmt.Errorf("can't unmarshal split info from root index: %w", err)
 	}