Issue #3035980 by jhedstrom: Provide a better error when a NULL is passed to...

Issue #3035980 by jhedstrom: Provide a better error when a NULL is passed to EntityStorageBase::load()

(cherry picked from commit 4dfdaaed)

core/lib/Drupal/Core/Entity/EntityStorageBase.php

@@ -246,6 +246,7 @@ protected function doCreate(array $values) {
    * {@inheritdoc}
    */
   public function load($id) {
+    assert(!is_null($id), 'Cannot load a NULL ID.');
     $entities = $this->loadMultiple([$id]);
     return isset($entities[$id]) ? $entities[$id] : NULL;
   }

core/tests/Drupal/Tests/Core/Config/Entity/ConfigEntityStorageTest.php

@@ -559,6 +559,9 @@ public function testLoad() {
     $entity = $this->entityStorage->load('foo');
     $this->assertInstanceOf(EntityInterface::class, $entity);
     $this->assertSame('foo', $entity->id());
+
+    $this->setExpectedException(\AssertionError::class, 'Cannot load a NULL ID.');
+    $this->entityStorage->load(NULL);
   }
 
   /**