fixed typo

src/Symfony/Bundle/FrameworkBundle/Controller/ExceptionController.php

@@ -47,7 +47,7 @@ class ExceptionController extends ContainerAware
         if ($this->container->get('kernel')->isDebug() && 'html' == $format) {
             $name = 'exception_full';
         }
-        $template = 'FrameworkBundle:Exception:'.$name.$format.'.twig';
+        $template = 'FrameworkBundle:Exception:'.$name.'.'.$format.'.twig';
 
         $templating = $this->container->get('templating');
         if (!$templating->exists($template)) {