My website is running TYPO3 v12.
I want to create a very simple widget in order to display a text in the dashboard. I read and follow this tutorial and the official Typo3 dashboard doc but I get error 500.

ClassesWidgetCustomWidget.php

<?php
    class CustomWidget implements WidgetInterface
    {
       /**
        * @var WidgetConfigurationInterface
        */
       private $configuration;
    
       /**
        * @var StandaloneView
        */
       private $view;
    
       /**
        * @var Cache
        */
       private $cache;
    
       /**
        * @var array
        */
       private $options;
    
       /**
        * @var ButtonProviderInterface|null
        */
       private $buttonProvider;
    
       public function __construct(
           WidgetConfigurationInterface $configuration,
           Cache $cache,
           StandaloneView $view,
           ButtonProviderInterface $buttonProvider = null,
           array $options = []
       ) {
           $this->configuration = $configuration;
           $this->view = $view;
           $this->cache = $cache;
           $this->buttonProvider = $buttonProvider;
       }
    
       public function renderWidgetContent(): string
       {
           $this->view->setTemplate('Widget/CustomWidget');
           $this->view->assignMultiple([
               'items' => 'Wow! Looks Amazing Widget!',
               'button' => $this->getButton(),
               'configuration' => $this->configuration,
           ]);
           return $this->view->render();
       }
    }

ConfigurationServices.yaml

services:
  _defaults:
    autowire: true
    autoconfigure: true
    public: false

  MyCompany:
    resource: '../Classes/*'
    
 TYPO3CMSDashboardWidgets:
   resource: '../Classes/Widgets/*'

 dashboard.buttons.custom:
   class: 'TYPO3CMSDashboardWidgetsProviderButtonProvider'
   arguments:
     $title: 'Custom Widget'
     $link: 'https://t3planet.com/'
     $target: '_blank'

 dashboard.widget.custom:
   class: 'MyCompanyWidgetCustomWidget'
   arguments:
     $view: '@dashboard.views.widget'
     $buttonProvider: '@dashboard.buttons.custom'
     $cache: '@cache.dashboard.rss'
   tags:
     - name: dashboard.widget
       identifier: 'custom'
       groupNames: 'general'
       title: 'Custom Widget'
       description: 'Wow! Looks Amazing Widget!'
       iconIdentifier: 'content-widget-rss'
       height: 'medium'
       width: 'medium'

When saving my xxx, TYPO3 front-end + back-end are broken with error 500.
My php_error.log (from WAMP) has this error:

PHP Fatal error:  Uncaught Error: Typed static property TYPO3CMSCoreUtilityExtensionManagementUtility::$packageManager must not be accessed before initialization in C:wamp64wwwmycompanyvendortypo3cms-coreClassesUtilityExtensionManagementUtility.php:111

I tried to create the widget without buttons and with minimal requirements, same error.