[#1261] shard: Fix delete objects from FSTree

Replace nil storageID with empty like by shard.Get.

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

pkg/local_object_storage/shard/delete.go

@@ -117,6 +117,12 @@ func (s *Shard) deleteFromBlobstor(ctx context.Context, addr oid.Address) error
 		return err
 	}
 	storageID := res.StorageID()
+	if storageID == nil {
+		// if storageID is nil it means:
+		// 1. there is no such object
+		// 2. object stored by writecache: should not happen, as `validateWritecacheDoesntContainObject` called before `deleteFromBlobstor`
+		return nil
+	}
 
 	var delPrm common.DeletePrm
 	delPrm.Address = addr