Update formatCurrency to handle optional currencyCode and default to EUR

app/lib/formatStrings.ts

@@ -1,4 +1,4 @@
-export const formatCurrency = (amount: number, currencyCode: string = "EUR") => {
+export const formatCurrency = (amount: number, currencyCode?: string | null) => {
     // format number with 2 decimal places and a thousand separator
     // amount is in cents
     const amountInUnits = amount / 100;
@@ -7,7 +7,7 @@ export const formatCurrency = (amount: number, currencyCode: string = "EUR") =>
     try {
         return new Intl.NumberFormat('hr-HR', {
             style: 'currency',
-            currency: currencyCode,
+            currency: currencyCode ?? "EUR",
             minimumFractionDigits: 2,
             maximumFractionDigits: 2,
         }).format(amountInUnits);