Added create contact ednpoint

database/invoice/invoice.go

@@ -47,13 +47,15 @@ func GetInvoices(buyerName string, sortBy string, limit int, offset int, id uint
         Find(&invoices).Error; err != nil {
         return nil, 0, err
     }
-
+ 
     for i := range invoices {
         var sum int64
-        for _, item := range invoices[i].InvoiceItem {
+        if invoices[i].InvoiceItem != nil {
+        for _, item := range *invoices[i].InvoiceItem {
             sum += item.PriceCents * item.Quantity
         }
         invoices[i].PriceCents = sum
+        }
     }
 
     return invoices, total, nil