A服务RPC调用B服务找不到可用地址时，导致当前线程上下文被清除，接着再调用C服务时取CSE上下文报空指针异常

1、当前线程A服务代码中第73行使用RPC方式异步调用B服务：

2、负载均衡没有找到B服务可用的地址：

3、A服务当前线程上下文被清除：

4、A服务当前线程再接着调用C服务时，从上下文中获取参数时报空指针：

Start with the A-service code at line 73 and trace the thread-context handling when the load balancer finds no available B-service address. Reproduce the following C-service call and inspect the context lookup shown in the screenshots; done means the failure path no longer causes a null-pointer exception during the subsequent C call.

Written by the indexing model from the issue text.