Issue #3424878: Check if ignored_config_entities is null and return an array

config_ignore.install

@@ -36,7 +36,7 @@ function config_ignore_update_8301() {
  */
 function config_ignore_update_8302() {
   $config = \Drupal::configFactory()->getEditable('config_ignore.settings');
-  $object = new ConfigIgnoreConfig('simple', $config->get('ignored_config_entities'));
+  $object = new ConfigIgnoreConfig('simple', $config->get('ignored_config_entities') ?? []);
   // Save the config with the mode set and the settings sorted.
   $config->set('mode', 'simple');
   $config->set('ignored_config_entities', $object->getFormated('simple'));