brpc在ProcessMongoRequest函数中出现coredump

**Describe the bug (描述bug)**

brpc在ProcessMongoRequest函数中出现coredump
**To Reproduce (复现方法)**

暂时没有复现方法
**Expected behavior (期望行为)**

-
**Versions (各种版本)**
OS:
Compiler:
brpc:
0.9.7
protobuf:

**Additional context/screenshots (更多上下文/截图)**

Start by locating the ProcessMongoRequest entry point in the brpc source and reviewing the attached coredump screenshot. The issue provides no reproduction steps or expected behavior, so first obtain a usable stack trace or reproduction; completion requires identifying and preventing the crash with validation against the reported failure.

Written by the indexing model from the issue text.