Issue #2864922 by vaplas, dawehner, Lendude: \Drupal\views\Plugin\views\display\EntityReference::render returns the wrong datatype for empty results

core/modules/views/src/Plugin/views/display/EntityReference.php

@@ -90,13 +90,16 @@ class EntityReference extends DisplayPluginBase {
   }
 
   /**
-   * {@inheritdoc}
+   * Builds the view result as a renderable array.
+   *
+   * @return array
+   *   Renderable array or empty array.
    */
   public function render() {
     if (!empty($this->view->result) && $this->view->style_plugin->evenEmpty()) {
       return $this->view->style_plugin->render($this->view->result);
     }
-    return '';
+    return [];
   }
 
   /**

core/modules/views/tests/src/Functional/Plugin/DisplayEntityReferenceTest.php

@@ -249,6 +249,12 @@ class DisplayEntityReferenceTest extends ViewTestBase {
     $this->executeView($view);
 
     $this->assertEqual(count($view->result), 2, 'Search returned two rows');
+
+    // Test that the render() return empty array for empty result.
+    $view = Views::getView('test_display_entity_reference');
+    $view->setDisplay('entity_reference_1');
+    $render = $view->display_handler->render();
+    $this->assertSame([], $render, 'Render returned empty array');
   }
 
 }