Resolve #3496037: Fix implicitly nullable type hints

Closes #3496037

src/Entity/Search.php

@@ -296,7 +296,7 @@ class Search extends ConfigEntityBase implements SearchInterface {
   /**
    * {@inheritdoc}
    */
-  public function setSuggesters(array $suggesters = NULL) {
+  public function setSuggesters(?array $suggesters = NULL) {
     $this->suggesterInstances = $suggesters;
 
     // Sanitize the suggester weights and limits.