[HttpKernel] fixed a crash on some machines (check that the controller is actually a class name before calling method_exists, closes #769)

src/Symfony/Component/HttpKernel/Controller/ControllerResolver.php

@@ -60,7 +60,7 @@ class ControllerResolver implements ControllerResolverInterface
             return false;
         }
 
-        if (is_array($controller) || method_exists($controller, '__invoke')) {
+        if (is_array($controller) || ((is_object($controller) || false === strpos($controller, ':')) && method_exists($controller, '__invoke'))) {
             return $controller;
         }