Update method parameter type in ExportController

The parameter type for the 'rebuildRawData' function in the ExportController class has been changed to accept null values. This change is introduced to handle cases where a null key might be passed, preventing potential errors in the application.

src/Bundle/ChillMainBundle/Controller/ExportController.php

@@ -632,7 +632,7 @@ class ExportController extends AbstractController
         }
     }
 
-    private function rebuildRawData(string $key): array
+    private function rebuildRawData(?string $key): array
     {
         if (null === $key) {
             throw $this->createNotFoundException('key does not exists');