Draft: Issue #3302838: Querying with NULL values results in warning mb_strtolower(): Passing null to parameter is deprecated

Closes #3302838

core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php

@@ -306,12 +306,14 @@ public function preSave(EntityStorageInterface $storage) {
 
     // Ensure this entity's UUID does not exist with a different ID, regardless
     // of whether it's new or updated.
-    $matching_entities = $storage->getQuery()
-      ->condition('uuid', $this->uuid())
-      ->execute();
-    $matched_entity = reset($matching_entities);
-    if (!empty($matched_entity) && ($matched_entity != $this->id()) && $matched_entity != $this->getOriginalId()) {
-      throw new ConfigDuplicateUUIDException("Attempt to save a configuration entity '{$this->id()}' with UUID '{$this->uuid()}' when this UUID is already used for '$matched_entity'");
+    if ($this->uuid() !== NULL) {
+      $matching_entities = $storage->getQuery()
+        ->condition('uuid', $this->uuid())
+        ->execute();
+      $matched_entity = reset($matching_entities);
+      if (!empty($matched_entity) && ($matched_entity != $this->id()) && $matched_entity != $this->getOriginalId()) {
+        throw new ConfigDuplicateUUIDException("Attempt to save a configuration entity '{$this->id()}' with UUID '{$this->uuid()}' when this UUID is already used for '$matched_entity'");
+      }
     }
 
     // If this entity is not new, load the original entity for comparison.