Fixed BillLineStore SQL logic error

prs.stores/BillLineStore.cs

@@ -14,7 +14,7 @@ namespace Comal.Stores
                 new Columns<PurchaseOrderItem>(
                     x => x.ID,
                     x => x.ExTax,
-                    x => x.TaxCode,
+                    x => x.TaxCode.ID,
                     x => x.TaxRate,
                     x => x.IncTax,
                     x => x.Balance,