Erro "Failed opening required bootstrap/../vendor/autoload.php" no Laravel 5

Olá a todos! Sou novo no Laravel 5 e PHP. Instalei o framework via Composer, mas ao tentar executar o projeto com `php artisan serve` ou simplesmente abrir no navegador, recebo um erro fatal:\n\n```\nFatal error: require(): Failed opening required 'C:\\xampp\\htdocs\\myproject\\bootstrap/../vendor/autoload.php' (include_path='C:\\xampp\\htdocs\\myproject\\vendor\\composer/../../..') in C:\\xampp\\htdocs\\myproject\\bootstrap\\autoload.php on line 17\n```\n\nAqui está o código do arquivo `bootstrap/autoload.php` (linha 17):\n\n```php\n