Fail when loading a model

Hi, I'm trying to make a record.
I refer to here on the official page.
create-a-form

• point A is OK. simple page
  
• point B is NG. number_format(): Passing null to parameter #1 ($num) of type float is deprecated
  
• If I comment out point B, the page will be displayed. simple creatable page
  

Why am I getting this error even though I'm loading the exact same model?

PHP Code:

(SchoolLessonController.php)
class SchoolLessonController extends BaseController
{
    /**
    * @return string
    */
    public function index(): string
    {
        $model = model(LessonModel::class);      // <- point A
        $data['lessons'] = $model->findAll();
        
        // List of grades
        return view("school/lesson/list", $data);
    }
    
    /** 
    * @param int $groupId
    * @return string
    */
    public function detail(int $groupId): string
    {
        $data = ["group_id" => $groupId];
    
        // Details of a class
        return view("school/lesson/detail", $data);
    }
    
    /**
    * @throws ReflectionException
    */
    public function create(): RedirectResponse|string
    {
        $model = model(LessonModel::class);     // <- point B
        $rules = [
            'title' => 'required|min_length[3]|max_length[255]',
            'body'  => 'required',
        ];
        
        if ($this->request->getMethod() === 'post' && $this->validate($rules)) {
            $data = [
                'title' => $this->request->getPost('title'),
                'body' => $this->request->getPost('body'),
            ];
            $model->save($data);
        
            // If you want to create continuously, redirect to create. If not, redirect to list.
            return redirect('school/lesson/create/success', $data);
        } else {
            $data = [
                'title' => null,
                'body' => null,
            ];
        }
    
        return view('school/lesson/create', $data);
    }
} 


Update CI version to 4.1.9

Update CI version to 4.1.9

thanks, iRedds. Thank you as always.

exact it was fixed. my codeigniter version had 4.1.6