key with '.' in it, creates nested key

[sebastiaanspeck]

Laravel Version: 5.7.9
PHP Version: 7.1.19
Database Driver & Version: MySQL 5.7.23

Description:

When you have a key in a language-file with a . (e.a. 'No.' in it and run php artisan langman:sync and a language is missing that key, it doesn't add the key the same way but changes it to:

    'No' => [
        '' => '',
    ],

instead of

    'No.' => '',

Steps to reproduce:

See description