fix error page code 404 can not CMS preview

src/Middleware/LocaleSwitchRedirector.php

@@ -32,6 +32,7 @@ public function process(HTTPRequest $request, callable $delegate)
         if ($response->getStatusCode() === 404
             && !$state->getIsFrontend()
             && $this->getParamLocale($request)
+            && !$request->getVar('CMSPreview')
         ) {
             // Redirect to the CMS home page if the requested page doesn't exist
             $response = new HTTPResponse();