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Cannot read properties of undefined (reading 'content-type') using express js

See original GitHub issue

Environment

Operating System: Linux
Node Version: v16.10.0
Nuxt Version: 3.0.0-27265876.3cd4494
Package Manager: yarn@1.22.17
Bundler: Vite
User Config: serverMiddleware
Runtime Modules: -
Build Modules: -

Describe the bug

serverMiddleware doesn’t work with express.js (4.17.1) and throws “Cannot read properties of undefined (reading 'content-type')” error

Reproduction

Clone a repository with the bug and run it as dev server

$ git clone https://github.com/martiliones/nuxt-express-bug
$ cd nuxt-express-bug && yarn install
$ yarn dev

Open http://localhost:3000/projects/ in your browser

Additional context

I tested serverMiddleware with h3 and it works just fine:

// api/index.js
import { createApp } from 'h3'

const app = createApp()
app.use('/projects', () => JSON.stringify([
    {
      name: 'asdsad',
      type: ['asdsad', 'asdsad']
    }
]))

Logs

Cannot read properties of undefined (reading 'content-type')
  at ServerResponse.getHeader (node:_http_outgoing:597:24)  
  at ServerResponse.res.get (./node_modules/express/lib/response.js:789:15)  
  at ServerResponse.json (./node_modules/express/lib/response.js:263:13)  
  at file://./.nuxt/nitro/index.mjs:139:7  
  at Layer.handle [as handle_request] (./node_modules/express/lib/router/layer.js:95:5)  
  at next (./node_modules/express/lib/router/route.js:137:13)  
  at Route.dispatch (./node_modules/express/lib/router/route.js:112:3)  
  at Layer.handle [as handle_request] (./node_modules/express/lib/router/layer.js:95:5)  
  at ./node_modules/express/lib/router/index.js:281:22  
  at Function.process_params (./node_modules/express/lib/router/index.js:335:12)