Return empty strings for batch and copyright (#31)

src/datasources/product-api.ts

@@ -104,6 +104,8 @@ export class ProductAPI extends BaseSQLDataSource {
     row.fields = this.getProductFields(row);
     row.designerId = row.designerid;
     row.orientation = this.getOrientation(row.fields);
+    row.copyright = row.copyright ?? '';
+    row.batch = row.batch ?? '';
     return row;
   }