fix: 处理null问题

buhuazhen

2026-06-01 facbfd2b1a0eb1ea971b699def8c85a43c5fa7fa

 src/main/java/com/ruoyi/purchase/dto/PaymentLedgerDto.java

@@ -8,6 +8,8 @@
    // 供应商名称
    private String supplierName;

    private Long supplierId;

    // 开始日期
    private String startDate;