unified return null usages

src/Symfony/Bridge/Doctrine/ExpressionLanguage/DoctrineParserCache.php

@@ -36,7 +36,7 @@ class DoctrineParserCache implements ParserCacheInterface
     public function fetch($key)
     {
         if (false === $value = $this->cache->fetch($key)) {
-            return null;
+            return;
         }
 
         return $value;

src/Symfony/Bridge/Propel1/Tests/Fixtures/ItemQuery.php

@@ -93,8 +93,6 @@ class ItemQuery
         if (isset($this->caseInsensitiveMap[$column])) {
             return $this->getColumn($this->caseInsensitiveMap[$column]);
         }
-
-        return null;
     }
 
     /**

src/Symfony/Bundle/FrameworkBundle/EventListener/SessionListener.php

@@ -34,7 +34,7 @@ class SessionListener extends BaseSessionListener
     protected function getSession()
     {
         if (!$this->container->has('session')) {
-            return null;
+            return;
         }
 
         return $this->container->get('session');

src/Symfony/Bundle/FrameworkBundle/EventListener/TestSessionListener.php

@@ -31,7 +31,7 @@ class TestSessionListener extends BaseTestSessionListener
     protected function getSession()
     {
         if (!$this->container->has('session')) {
-            return null;
+            return;
         }
 
         return $this->container->get('session');

src/Symfony/Component/DependencyInjection/ContainerBuilder.php

@@ -481,7 +481,7 @@ class ContainerBuilder extends Container implements TaggedContainerInterface
                 $definition = $this->getDefinition($id);
             } catch (InvalidArgumentException $e) {
                 if (ContainerInterface::EXCEPTION_ON_INVALID_REFERENCE !== $invalidBehavior) {
-                    return null;
+                    return;
                 }
 
                 throw $e;

src/Symfony/Component/HttpFoundation/RequestStack.php

@@ -47,7 +47,7 @@ class RequestStack
     public function pop()
     {
         if (!$this->requests) {
-            return null;
+            return;
         }
 
         return array_pop($this->requests);
@@ -73,7 +73,7 @@ class RequestStack
     public function getMasterRequest()
     {
         if (!$this->requests) {
-            return null;
+            return;
         }
 
         return $this->requests[0];
@@ -95,7 +95,7 @@ class RequestStack
         $pos = count($this->requests) - 2;
 
         if (!isset($this->requests[$pos])) {
-            return null;
+            return;
         }
 
         return $this->requests[$pos];