Empty JSON object does not get fixed by fixRequestBody

[mhassan1]

yarn why http-proxy-middleware OR npm ls http-proxy-middleware output (mask private folder names with *****)

├─ server@workspace:packages/server
│  └─ http-proxy-middleware@npm:2.0.1 (via npm:^2.0.1)

• I understand project setup issues should be asked on StackOverflow or in GitHub Discussions.
• I updated to latest http-proxy-middleware.

Describe the bug (be clear and concise)

The fixRequestBody utility contains a check for empty objects that results in early return:

http-proxy-middleware/src/handlers/fix-request-body.ts

Lines 11 to 13 in c9bec81

	if (!requestBody || !Object.keys(requestBody).length) {
	return;
	}

When an empty object request (curl ... -H 'content-type: application/json' -d '{}') is made to a proxy with onProxyReq: fixRequestBody, the request hangs because the target is expecting content-length: 2 but never receives any payload because of the early return. See Steps to Reproduce, below.

Am I missing a reason why empty objects get special handling?

Step-by-step reproduction instructions

1. Run the following script:

const express = require('express')
const bodyParser = require('body-parser')
const { createProxyMiddleware, fixRequestBody } = require('http-proxy-middleware')

const proxyApp = express()
proxyApp.use(bodyParser.json())
proxyApp.use(createProxyMiddleware({
  target: 'http://localhost:8081',
  onProxyReq: fixRequestBody
}))
proxyApp.listen(8080)

const app = express()
app.use((req, res, next) => console.log(req.headers) || next())
app.use(bodyParser.json())
app.post('/', (req, res) => res.json(req.body))
app.listen(8081)

2. `curl localhost:8080 -XPOST -H 'content-type: application/json' -d '{"hello":"there"}'` -> `{"hello":"there"}`
3. `curl localhost:8080 -XPOST -H 'content-type: application/json' -d '{}'` -> hangs

Expected behavior (be clear and concise)

I expect an empty object JSON request to be proxied with the request body fixed, the same way as a non-empty object JSON request.

What http-proxy-middleware configuration are you using?

const { createProxyMiddleware, fixRequestBody } = require('http-proxy-middleware')

app.use(createProxyMiddleware({
  target: 'http://localhost:8081',
  onProxyReq: fixRequestBody
}))

What OS/version and node/version are you seeing the problem?

MacOS 11.4 and Node 14.15.1

Additional context (optional)

No response