TYPO3 Core

The only feedback I get is like "An error occured while calling the \Clickstorm\CsExample\Domain\Model\Item->showAction()".

My workaround now is:

         /**
     * action show
     *
     * @param \Clickstorm\CsExample\Domain\Model\Item $item
     * @return void
     */
    public function showAction(\Clickstorm\CsExample\Domain\Model\Item $item) {
        $this->view->assign('item', $item);
    }

change in:

/**
     * action show
     *
     * @return void
     */
    public function showAction()
    {
        if($this->request->hasArgument('item')) {
            $concert = $this->citemRepository->findByUid($this->request->getArgument('item'));
            $this->view->assign('item', $item);
        }

    }

If I change this it works. I had the problem in two projects with TYPO3 6.2.21 with two different extensions. Other extensions that are installed and have a show action worked until now, that is confusing. 6.2.22 I can't install because of the broken select tree. Any solutions?