laravel error: Trying to get property of non-object (View: C:\laragon\www\al-Zad\resources\views\blog\index.blade.php)

I'm using laravel and i get this error:

Trying to get property of non-object (View: C:\laragon\www\al-Zad\resources\views\blog\index.blade.php)

the problem is in this line:

this are the models:

namespace App;

use Illuminate\Database\Eloquent\Model;

post model:

namespace App;

use Illuminate\Database\Eloquent\Model;

class post extends Model {

public function author()
{
    return $this->belongsTo(User::class);
}

}

User model:

namespace App;

use Illuminate\Notifications\Notifiable; use Illuminate\Foundation\Auth\User as Authenticatable;

class User extends Authenticatable { use Notifiable;

/**
 * The attributes that are mass assignable.
 *
 * @var array
 */
protected $fillable = [
    'name', 'email', 'password',
];

/**
 * The attributes that should be hidden for arrays.
 *
 * @var array
 */
protected $hidden = [
    'password', 'remember_token',
];

public function posts()
{
 return $this->hasMany(post::class);   
}

}

Thanks for your help

via mohammed