[Flow] Fatal error: help please

[Richard Benson]

I have just started running through the documentation in an effort to try and gain a greater understanding of this platform.

Fatal error: Call to a member function getTitle() on a non-object in C:\xampp\htdocs\tutorial\Data\Temporary\Development\Cache\Code\Flow_Object_Classes\TYPO3_Blog_Controller_PostController.php on line 29

public function indexAction() {
	         $blog = $this->blogRepository->findActive();
                $output = '
                        <h1>Posts of "' . $blog->getTitle() . '"</h1> Line 29
                        <ol>';

                foreach ($blog->getPosts() as $post) {
                        $output .= '<li>' . $post->getTitle() . '</li>';
                }

                $output .= '</ol>';

                return $output;
        }

What is this error and what do I need to do to fix it.

Kind Regards

Richard