Error at redirecting throught beforeEach

[JFGHT]

Version

3.1.3

Reproduction link

https://github.com/JFGHT/vue-router-error-repro

Steps to reproduce

1.- Push to any route (this.$router.push('/test');).
2.- Redirect to same router but with extra param.

if (to.fullPath === '/test') {
  next('/en/test');
}

route:

{
  path: '/:lang?/test',
  name: 'test',
  component: () => import(/* webpackChunkName: "test" */ './views/Test.vue'),
},

What is expected?

Correct redirect.

What is actually happening?

It's redirecting but it's displaying an error:
vue-router.esm.js?8c4f:2051 Uncaught (in promise) undefined

[posva]

See #2873 (comment)