Add PHPStan configuration for Symfony4 tests

- Created a new phpstan.neon file in the Symfony4 tests directory.
- Configured paths and excluded Symfony3 directory.
- Added bootstrap files for autoloading.
- Set dynamic constant names and adjusted reporting settings.
- Established PHPStan level to 6 for stricter analysis.

modules/empikmarketplace/controllers/admin/AdminEmpikActionLogController.php

@@ -204,7 +204,10 @@ class AdminEmpikActionLogController extends ModuleAdminController
      */
     protected function contentOutput($content, $filename = 'error_report.csv')
     {
-        ob_clean();
+        if (ob_get_level() > 0) {
+            ob_clean();
+        }
+
         header('Content-Type: application/octet-stream');
         header('Content-Disposition: attachment; filename="'.$filename.'"');
         header('Content-Length: ' . strlen($content));