fix(dashboard): nan in tax total (#13699)

CLOSES CORE-1210

packages/admin/dashboard/src/routes/orders/order-detail/components/order-summary-section/order-summary-section.tsx

@@ -575,9 +575,10 @@ const CostBreakdown = ({
 
     order.items.forEach((item) => {
       item.tax_lines?.forEach((line) => {
+        const currTotal = line.subtotal || 0
         const prevTotal = taxCodeMap[line.code]?.total || 0
         taxCodeMap[line.code] = {
-          total: prevTotal + line.subtotal,
+          total: prevTotal + currTotal,
           rate: line.rate,
         }
       })
@@ -585,9 +586,10 @@ const CostBreakdown = ({
 
     order.shipping_methods.forEach((sm) => {
       sm.tax_lines?.forEach((line) => {
+        const currTotal = line.subtotal || 0
         const prevTotal = taxCodeMap[line.code]?.total || 0
         taxCodeMap[line.code] = {
-          total: prevTotal + line.subtotal,
+          total: prevTotal + currTotal,
           rate: line.rate,
         }
       })