Enable winguist_ui_patterns without proper theme gives an unexpected error.

Problem/Motivation

I’m experiencing an issue when enabling the module `winguist_ui_patterns` in D9 = `The website encountered an unexpected error. Please try again later.`.

Watchdog gives me this message after the module has been installed: `2010 17/Aug 07:53 php Error Drupal\Core\File\Exception\NotRegularDirectoryException: is not a directory. in Drupal\Core\File\FileSystem->scanDirectory() (line 665 of /app/web/core/lib/Drupal/Core/File/FileSystem.php`

Steps to reproduce

Enable the module `winguist_ui_patterns` without having a wingsuit theme.

Proposed resolution

See patch.

Remaining tasks

User interface changes

API changes

Data model changes