Steps to reproduce the issue

1. On a JP Pro site, enable "Search".
2. Add a JP search widget.
3. Put the site in the development mode - https://jetpack.com/support/development-mode/
4. See the front-end.

What I expected

No error.

What happened instead

A fatal error.

PHP Fatal error: Uncaught Error: Class 'Jetpack_Search_Template_Tags' not found in /wordpress/plugins/jetpack/6.7/modules/widgets/search.php:324