Fix PHP8.2 deprecations.

Closes #3384604

src/Plugin/views/field/ViewsJsonField.php

@@ -15,6 +15,13 @@ use Drupal\Core\Render\Markup;
  */
 class ViewsJsonField extends FieldPluginBase {
 
+  /**
+   * The table alias.
+   *
+   * @var string
+   */
+  public $table_alias = '';
+
   /**
    * Render.
    */