fix: 处理空值计算，确保待来票金额与未来票金额一致

gongchunyi

2026-01-16 79a570ae5f497e30337e7dd002450072e1b21cc2

 src/main/java/com/ruoyi/purchase/pojo/ProductRecord.java

@@ -35,6 +35,11 @@
    private Long purchaseLedgerId;

    /**
     * 产品id
     */
    private Long saleLedgerProjectId;

    /**
     * 产品大类
     */
    private String productCategory;