Issue #3045273 by tatarbj, heddn, mlhess, catch: Add real endpoint after...

Issue #3045273 by tatarbj, heddn, mlhess, catch: Add real endpoint after drupal.org provides a live feed

config/install/automatic_updates.settings.yml

-# Public service announcement URI endpoint.
-# TODO:  Update to correct end point once it is available. See
-# https://www.drupal.org/project/automatic_updates/issues/3045273
-psa_endpoint: 'http://example.com/automatic_updates/test-json'
+psa_endpoint: 'https://updates.drupal.org/psa.json'
 enable_psa: true
 notify: true
 check_frequency: 43200

src/Services/AutomaticUpdatesPsa.php

@@ -136,7 +136,7 @@ class AutomaticUpdatesPsa implements AutomaticUpdatesPsaInterface {
 
     try {
       $json_payload = json_decode($response);
-      if ($json_payload) {
+      if (!is_null($json_payload)) {
         foreach ($json_payload as $json) {
           if ($json->is_psa && ($json->type === 'core' || $this->isValidExtension($json->type, $json->project))) {
             $messages[] = $this->message($json->title, $json->link);