Accessing Non-Existent Pages Does Not Return HTTP 404 Status Code

[shunshimono]

Describe the bug
Accessing a non-existent page does notreturn an HTTP 404 status code. Instead, it returns a 200 status code, which can lead to issues with SEO and proper error handling.

To Reproduce

1. Set up a Next.js project using next-international.(Custom 404 Page set)
2. Start the development server.
3. Navigate to a URL that does not correspond to any existing page or route (e.g., http://localhost:3000/non-existent-page).
4. Observe that the page loads without displaying a 404 error, and the HTTP status code is 200.

app
├── [local]
  └── not-found.tsx
  └── [...other]
        └── page.tsx

[...other]/page.tsx

import { notFound } from 'next/navigation';

export default function CatchAllPage() {
  notFound();
}

middleware.ts

import type { NextRequest } from 'next/server';
import { createI18nMiddleware } from 'next-international/middleware';

const I18nMiddleware = createI18nMiddleware({
  locales: ['ja', 'en'],
  defaultLocale: 'ja',
  urlMappingStrategy: 'rewriteDefault',
});

export function middleware(request: NextRequest) {
  return I18nMiddleware(request);
}

export const config = {
  matcher: ['/((?!api|static|.*\\..*|_next|favicon.ico|robots.txt).*)'],
};

Expected behavior
The application should return an HTTP 404 status code when a user accesses a non-existent page, displaying a 404 error page accordingly.

Screenshots
N/A

About (please complete the following information):

• next-international version [1.2.3]
• Next.js version [14.2.0]

Additional context
This issue affects error handling and SEO, as search engines might index non-existent pages due to the incorrect status code

[MemoS77]

Same problem. No 404 code. Always 200...

import { createI18nMiddleware } from 'next-international/middleware'
import { NextRequest, NextResponse } from 'next/server'

export const defaultLocale = 'en'

const I18nMiddleware = createI18nMiddleware({
  locales: ['en', 'ru'],
  defaultLocale,  
})

export function middleware(request: NextRequest) {
return I18nMiddleware(request)
}

export const config = {
  matcher: ['/((?!api|static|.*\\..*|_next).*)'],
}