fix(oa):修复项目更新时客户ID为0的处理逻辑

- 修复了当客户ID为0时未正确设置为null的问题- 添加了对客户ID非空的前置判断，避免空指针异常

ruoyi-oa/src/main/java/com/ruoyi/oa/service/impl/SysOaProjectServiceImpl.java

@@ -227,7 +227,7 @@ public class SysOaProjectServiceImpl implements ISysOaProjectService {
         SysOaProject update = BeanUtil.toBean(bo, SysOaProject.class);
 
         // 当 customerId 为 0 时，设置为 null
-        if (bo.getCustomerId() == 0) {
+        if (bo.getCustomerId() != null && bo.getCustomerId() == 0) {
             update.setCustomerId(null);
         }