fix(wms): 修复审批列表为空时返回空指针异常

- 当审批列表为空时，创建并返回包含空记录的分页对象
- 设置分页参数包括总数、大小、当前页和页数
- 使用TableDataInfo构建返回结果避免空指针错误

klp-wms/src/main/java/com/klp/service/impl/WmsApprovalServiceImpl.java

@@ -89,7 +89,14 @@ public class WmsApprovalServiceImpl implements IWmsApprovalService {
         List<WmsApprovalVo> approvalList = approvalPage.getRecords();
 
         if (CollectionUtil.isEmpty(approvalList)) {
-            return null;
+            Page<Map<String, Object>> emptyResultPage = new Page<>();
+            emptyResultPage.setRecords(new ArrayList<>());
+            emptyResultPage.setTotal(approvalPage.getTotal());
+            emptyResultPage.setSize(approvalPage.getSize());
+            emptyResultPage.setCurrent(approvalPage.getCurrent());
+            emptyResultPage.setPages(approvalPage.getPages());
+
+            return TableDataInfo.build(emptyResultPage);
         }
 
         // 2. 处理审批列表，拼接请假/外出详情，并收集所有需要转换的创建人账号