fix: ERP统计查询在多租户关闭时的NullPointerException问题

- 修复ErpSaleStatisticsMapper.xml中硬编码使用getRequiredTenantId()导致的空指针异常
- 修复ErpPurchaseStatisticsMapper.xml中硬编码使用getRequiredTenantId()导致的空指针异常
- 使用条件判断getTenantId() != null来决定是否添加租户条件
- 添加单元测试验证多租户开启和关闭时的统计查询功能
- 确保向后兼容，多租户开启时正常工作，关闭时不报错

yudao-module-erp/src/main/resources/mapper/statistics/ErpSaleStatisticsMapper.xml

@@ -10,7 +10,9 @@
                <if test="endTime != null">
                    AND out_time &lt; #{endTime}
                </if>
-               AND tenant_id = ${@cn.iocoder.yudao.framework.tenant.core.context.TenantContextHolder@getRequiredTenantId()}
+               <if test="@cn.iocoder.yudao.framework.tenant.core.context.TenantContextHolder@getTenantId() != null">
+                   AND tenant_id = ${@cn.iocoder.yudao.framework.tenant.core.context.TenantContextHolder@getTenantId()}
+               </if>
                AND deleted = 0) -
             (SELECT IFNULL(SUM(total_price), 0)
                 FROM erp_sale_return
@@ -18,7 +20,9 @@
                 <if test="endTime != null">
                     AND return_time &lt; #{endTime}
                 </if>
-                AND tenant_id = ${@cn.iocoder.yudao.framework.tenant.core.context.TenantContextHolder@getRequiredTenantId()}
+                <if test="@cn.iocoder.yudao.framework.tenant.core.context.TenantContextHolder@getTenantId() != null">
+                    AND tenant_id = ${@cn.iocoder.yudao.framework.tenant.core.context.TenantContextHolder@getTenantId()}
+                </if>
                 AND deleted = 0)
     </select>