added missing use statement.

extensions/gii/generators/crud/templates/controller.php

@@ -29,6 +29,7 @@ echo "<?php\n";
 
 namespace <?= StringHelper::dirname(ltrim($generator->controllerClass, '\\')) ?>;
 
+use Yii;
 use <?= ltrim($generator->modelClass, '\\') ?>;
 use <?= ltrim($generator->searchModelClass, '\\') ?><?php if (isset($searchModelAlias)):?> as <?= $searchModelAlias ?><?php endif ?>;
 use <?= ltrim($generator->baseControllerClass, '\\') ?>;