When webp_uploads_prefer_smaller_image_file is set to true, an undefine error occurs #396

Bug Description

It generate undefine variable error when webp_uploads_prefer_smaller_image_file is set to true.
#7 (comment)

Steps to reproduce

1. Add add_filter( 'webp_uploads_prefer_smaller_image_file', '__return_true' ); in theme or plugin
2. Upload image from this comment
3. See error

Error Message

Notice: Undefined variable: size_data in /var/www/html/wp-content/plugins/performance/modules/images/webp-uploads/load.php on line 484

Additional Context

• PHP Version: 7.4.30
• OS: Windows 10
• Browser: Chrome
• Plugin Version: 1.2.0
• Device: Desktop