laravel 提交空字符串会被转成 null 解决方法
将 app\Http\Kernel.php 标红色的类注销掉就可以了
protected $middleware = [
\App\Http\Middleware\CheckForMaintenanceMode::class,
\Illuminate\Foundation\Http\Middleware\ValidatePostSize::class,
\App\Http\Middleware\TrimStrings::class,
//\Illuminate\Foundation\Http\Middleware\ConvertEmptyStringsToNull::class,
\App\Http\Middleware\TrustProxies::class,
CrossRequest::class,
FilterParams::class,
];
