未定义的变量：在laravel中使用bootstrap组件时出现类错误

We are trying use bootstrap components for our fresh laravel project.

GitHub: https://github.com/appstract/laravel-bootstrap-components

we have following code in blade. but it doesn't work and have error.

blade codes:

@extends('layouts.app')
@section('page-title','Welcome')

@section('content')
    @component('bootstrap::alert', ['type' => 'danger'])
        A simple alert of danger type
    @endcomponent
@stop

error:

ErrorException (E_ERROR) Undefined variable: class (View: B:\xampp\htdocs\me2weesources\views\vendor\bootstrap\alert.blade.php) (View: B:\xampp\htdocs\me2weesources\views\vendor\bootstrap\alert.blade.php)

what we have to do to fix it?

It seems alert.blade.php contains the following snippet:

{{ $class or '' }}

The latest version of Laravel no longer supports or between curly brackets in blade. These have been replaced by PHP 7's null coalesce operator.

So it should now be like this:

{{ $class ?? '' }}

More info: https://laravel-news.com/blade-templates-null-coalesce-operator