Update Arr.php: Solve PHP Warning

When error_reporting = E_ALL
Raises fowling warning:

PHP Warning:  Invalid argument supplied for foreach() in /www/vendor/laravel/framework/src/Illuminate/Support/Arr.php on line 71
PHP Stack trace:
PHP   1. {main}() /www/artisan:0
PHP   2. require_once() /www/artisan:30
PHP   3. require() /www/bootstrap/start.php:57
PHP   4. Illuminate\Config\EnvironmentVariables->load() /www/vendor/laravel/framework/src/Illuminate/Foundation/start.php:120
PHP   5. Illuminate\Config\FileEnvironmentVariablesLoader->load() /www/vendor/laravel/framework/src/Illuminate/Config/EnvironmentVariables.php:35
PHP   6. array_dot() /www/vendor/laravel/framework/src/Illuminate/Config/FileEnvironmentVariablesLoader.php:49
PHP   7. Illuminate\Support\Arr::dot() /www/vendor/laravel/framework/src/Illuminate/Support/helpers.php:136