Issue #3475008 by viniciusrp: Applied configuration don't registered

Closes #3475008

src/ConfigInstaller.php

@@ -138,7 +138,8 @@ class ConfigInstaller extends OriginalConfigInstaller {
         $this->updater->doExecuteUpdate($data["items"]);
       }
 
-      $alterations_applied->set("files", $alterations_applied->get("files") + array_keys($config_to_alter))->save();
+      $applied_files = array_merge($alterations_applied->get("files"), array_keys($config_to_alter));
+      $alterations_applied->set("files", $applied_files)->save();
     }
   }