Don't throw 500 error when Content-type is invalid (vercel#24818)

Fixes vercel#24768

## Bug

- [x] Related issues linked using `fixes #number`
- [x] Integration tests added

packages/next/next-server/server/api-utils.ts

@@ -114,7 +114,12 @@ export async function parseBody(
   req: NextApiRequest,
   limit: string | number
 ): Promise<any> {
-  const contentType = parse(req.headers['content-type'] || 'text/plain')
+  let contentType
+  try {
+    contentType = parse(req.headers['content-type'] || 'text/plain')
+  } catch {
+    contentType = parse('text/plain')
+  }
   const { type, parameters } = contentType
   const encoding = parameters.charset || 'utf-8'
 

test/integration/api-body-parser/test/index.test.js

@@ -36,6 +36,13 @@ function runTests() {
     expect(data).toEqual([{ title: 'Nextjs' }])
     killApp(server)
   })
+
+  it("should not throw if request's content-type is invalid", async () => {
+    await startServer()
+    const status = await makeRequestWithInvalidContentType()
+    expect(status).toBe(200)
+    killApp(server)
+  })
 }
 
 async function makeRequest() {
@@ -50,6 +57,18 @@ async function makeRequest() {
   return data
 }
 
+async function makeRequestWithInvalidContentType() {
+  const status = await fetchViaHTTP(appPort, '/api', null, {
+    method: 'POST',
+    headers: {
+      'Content-Type': 'application/json;',
+    },
+    body: JSON.stringify([{ title: 'Nextjs' }]),
+  }).then((res) => res.status)
+
+  return status
+}
+
 const startServer = async (optEnv = {}, opts) => {
   const scriptPath = join(appDir, 'server.js')
   context.appPort = appPort = await getPort()