Made the router lazy when setting the context

Initializing the matcher and the generator to set the context does not make
sense as it is set anyway when building them. This avoids initializing
them in the RouterListener if you never actually use them (for instance
because you use the apache matcher).

src/Symfony/Component/Routing/Router.php

@@ -15,6 +15,8 @@
 use Symfony\Component\Config\ConfigCache;
 use Symfony\Component\HttpKernel\Log\LoggerInterface;
 use Symfony\Component\Routing\Generator\ConfigurableRequirementsInterface;
+use Symfony\Component\Routing\Generator\UrlGeneratorInterface;
+use Symfony\Component\Routing\Matcher\UrlMatcherInterface;
 
 /**
  * The Router class is an example of the integration of all pieces of the
@@ -150,8 +152,12 @@ public function setContext(RequestContext $context)
     {
         $this->context = $context;
 
-        $this->getMatcher()->setContext($context);
-        $this->getGenerator()->setContext($context);
+        if (null !== $this->matcher) {
+            $this->getMatcher()->setContext($context);
+        }
+        if (null !== $this->generator) {
+            $this->getGenerator()->setContext($context);
+        }
     }
 
     /**