Issue #1893844 by dawehner: Mark AreaPluginBase::render as abstract

core/modules/views/lib/Drupal/views/Plugin/views/area/AreaPluginBase.php

@@ -162,9 +162,7 @@ public function preRender(array $results) {
   /**
    * Render the area
    */
-  function render($empty = FALSE) {
-    return '';
-  }
+  public abstract function render($empty = FALSE);
 
   /**
    * Area handlers shouldn't have groupby.

core/modules/views/lib/Drupal/views/Plugin/views/area/Title.php

@@ -58,4 +58,11 @@ public function preRender(array $results) {
     return '';
   }
 
+  /**
+   * Implements \Drupal\views\Plugins\views\area\AreaPluginBase::render();
+   */
+  public function render($empty = FALSE) {
+    // Do nothing for this handler.
+  }
+
 }