JavaScript errors after clean install (TypeError: e is null, TypeError: this.flash is null)

I've just installed Statamic (tried creating a project and installing over a clean installation of Laravel 7) and after login in the control panel this errors appears:

TypeError: e is null
    u translator.js:49
    l translator.js:11
    __ globals.js:52
    __ mixins.js:13
    e mixins.js:7
    anonymous vendor.js:3
    VueJS 9
    start Statamic.js:74
    <anonymous> dashboard:402
vue.common.prod.js:6:11579

// 

TypeError: this.flash is null
    flashExistingMessages Toast.js:27
    mounted Toast.js:25
    VueJS 7
    start Statamic.js:74
    <anonymous> dashboard:402
vue.common.prod.js:6:11579
    VueJS 10
    start Statamic.js:74
    <anonymous> dashboard:402

After this error, all control panel dissapears so I can't do anything. I tried with npm run dev but nothing changes. I'm doing something wrong or must I open an issue on GitHub?.

The URL I'm using is http://localhost/testing/statamic/public/cp.