Fix check for empty string (#48)

Co-authored-by: deepsource-autofix[bot] <62050782+deepsource-autofix[bot]@users.noreply.github.com>

cmd/mytoken-server/mytoken-migratedb/version.go

@@ -97,7 +97,7 @@ func runAfterUpdates(tx *sqlx.Tx, afterDone map[string]bool) error {
 }
 func updateCallback(tx *sqlx.Tx, cmds, version string, done map[string]bool, dbUpdateCallback func(*sqlx.Tx, string) error) error {
 	log.WithField("version", version).Info("Updating DB to version")
-	if len(cmds) == 0 {
+	if cmds == "" {
 		return nil
 	}
 	if done[version] {