req.body lost its prototype after using multer

```
router.post('/upload', upload.single('file'), ((req, res, next) => {
logger.info('/upload enter');
logger.info('/upload reqFile: %s', req.file);
logger.info('/upload req.body: %s', req.body);
const params = tools.params(req)
logger.info('/upload params: %s; query: %s; body: %s; params: %s', params, req.query && req.query.name, req.body && req.body.name, req.params && req.params.name)
if (!params.name) {
res.json({
code: 400,
message: 'file must have a logic name',
sample: {
file: 'file, required',
name: 'string, required'
}
})
return
}
```

```
[ INFO] 2022-10-18 20:15:06 736 /upload req.body: [Object: null prototype] { name: 'test file' }
```

without multer, it is a normal object