Issue #3232420: Create a service which can recommend a target version of core

src/Form/UpdaterForm.php

@@ -92,7 +92,7 @@ class UpdaterForm extends FormBase {
       '#last' => $this->state->get('update.last_check', 0),
     ];
 
-    $project = NULL;
+    $project = [];
     try {
       $recommended_release = $recommender->getRecommendedRelease($project);
     }