Fixed a syntax issue

Author: javiereguiluz

components/error_handler.rst

@@ -135,7 +135,7 @@ PHP/XDebug output with something prettier and more useful.
 
 If the :doc:`HttpFoundation component </components/http_foundation>` is
 available, the handler returns a Symfony's
-:class:`Symfony\Component\HttpFoundation\Response` object. Otherwise, it returns
+:class:`Symfony\\Component\\HttpFoundation\\Response` object. Otherwise, it returns
 a generic PHP response.
 
 Use the following code (e.g. in your :ref:`front controller <architecture-front-controller>`)