[#288] pkg/eacl: Fix conversion of slices in Table.ToV2 method

Nil slice of records of the `Table` should be converted to nil slice in
corresponding field of API v2 message structure.

Add nil-check in `Table.ToV2` implementation. The changes fix corresponding
unit test.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/acl/eacl/table.go

@@ -88,13 +88,16 @@ func (t *Table) ToV2() *v2acl.Table {
 		v2.SetContainerID(t.cid.ToV2())
 	}
 
+	if t.records != nil {
 		records := make([]*v2acl.Record, 0, len(t.records))
 		for _, record := range t.records {
 			records = append(records, record.ToV2())
 		}
 
-	v2.SetVersion(t.version.ToV2())
 		v2.SetRecords(records)
+	}
+
+	v2.SetVersion(t.version.ToV2())
 
 	return v2
 }