Fixing issue with isValidFnr function that did not handle empty values as expected

frontend/src/utils/index.ts

@@ -43,8 +43,14 @@ export function submitJsonOpts(method: string, data: object): RequestInit {
   }
 }
 
-export function isValidFnr(data: string | undefined): boolean | string {
-  if (data === undefined) {
+export function isValidFnr(
+  data: string | undefined,
+  allowEmpty = false
+): boolean | string {
+  if (!data) {
+    if (allowEmpty) {
+      return true
+    }
     return i18n.t<string>('common:validation.invalidIdNumber').toString()
   }
   const valid = validator.idnr(data as string).status === 'valid'