diff --git a/src/interfaces/extension.ts b/src/interfaces/extension.ts
index 8a168442..5856f98e 100644
--- a/src/interfaces/extension.ts
+++ b/src/interfaces/extension.ts
@@ -230,9 +230,7 @@ class Extension {
 
   public static ToThaiShortYear(value: Date) {
     let yy = value.getFullYear() < 2400 ? value.getFullYear() + 543 : value.getFullYear();
-    return (
-      yy.toString()
-    );
+    return yy.toString();
   }
 
   public static sumObjectValues(array: any, propertyName: any) {
@@ -247,6 +245,9 @@ class Extension {
 
   public static CheckCitizen(value: string) {
     let citizen = value;
+    if (citizen == null || citizen == "") {
+      return citizen;
+    }
     if (citizen.length !== 13) {
       throw new HttpError(
         HttpStatus.NOT_FOUND,