Warning (2) : Attempt to read property "response" on null [in /var/www/clients/client3/web28/web/vendor/cakephp/cakephp/src/Controller/Controller.php, line 776]
Warning (512) : Unable to emit headers. Headers sent in file=/var/www/clients/client3/web28/web/vendor/cakephp/cakephp/src/Error/Renderer/HtmlErrorRenderer.php line=36 [in /var/www/clients/client3/web28/web/vendor/cakephp/cakephp/src/Http/ResponseEmitter.php, line 71]
Warning (2) : Cannot modify header information - headers already sent by (output started at /var/www/clients/client3/web28/web/vendor/cakephp/cakephp/src/Error/Renderer/HtmlErrorRenderer.php:36) [in /var/www/clients/client3/web28/web/vendor/cakephp/cakephp/src/Http/ResponseEmitter.php, line 168]
Warning (2) : Cannot modify header information - headers already sent by (output started at /var/www/clients/client3/web28/web/vendor/cakephp/cakephp/src/Error/Renderer/HtmlErrorRenderer.php:36) [in /var/www/clients/client3/web28/web/vendor/cakephp/cakephp/src/Http/ResponseEmitter.php, line 197]
Error: Controller class Pages could not be found.

Controller class Pages could not be found. 📋

Cake\Http\Exception\MissingControllerException
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    public function create(ServerRequestInterface $request): Controller
    {
        $className $this->getControllerClass($request);
        if ($className === null) {
            throw $this->missingController($request);
        }
        $reflection = new ReflectionClass($className);
        if ($reflection->isAbstract()) {

If you want to customize this error message, create templates/Error/error500.php