[FrameworkBundle] Fix wiring session.handler when handler_id is null

Author: nicolas-grekas

Session/Storage/Handler/NativeFileSessionHandler.php

@@ -49,7 +49,11 @@ public function __construct(string $savePath = null)
             throw new \RuntimeException(sprintf('Session Storage was not able to create directory "%s".', $baseDir));
         }
 
-        ini_set('session.save_path', $savePath);
-        ini_set('session.save_handler', 'files');
+        if ($savePath !== \ini_get('session.save_path')) {
+            ini_set('session.save_path', $savePath);
+        }
+        if ('files' !== \ini_get('session.save_handler')) {
+            ini_set('session.save_handler', 'files');
+        }
     }
 }

Session/Storage/NativeSessionStorage.php

@@ -455,9 +455,10 @@ public function setOptions(array $options)
      */
     public function setSaveHandler($saveHandler = null)
     {
-        if (!$saveHandler instanceof AbstractProxy &&
-            !$saveHandler instanceof \SessionHandlerInterface &&
-            null !== $saveHandler) {
+        if (!$saveHandler instanceof AbstractProxy
+            && !$saveHandler instanceof \SessionHandlerInterface
+            && null !== $saveHandler
+        ) {
             throw new \InvalidArgumentException('Must be instance of AbstractProxy; implement \SessionHandlerInterface; or be null.');
         }