tidb: Address comment

driver.go

@@ -389,7 +389,7 @@ func newdriverRows(rs rset.Recordset) *driverRows {
 // name isn't known, an empty string should be returned for that entry.
 func (r *driverRows) Columns() []string {
 	if r.rs == nil {
-		return make([]string, 0)
+		return []string{}
 	}
 	fs, _ := r.rs.Fields()
 	names := make([]string, len(fs))