[WP Smush Pro] Smush Pro, error message in logs, while smushing images.

Listing the error message here for you knowledge and future fix:

[22-Nov-2018 12:59:53 UTC] PHP Warning: Illegal string offset 'file' in /home/boutiquehomes/public_html/wp-content/plugins/wp-smush-pro/lib/class-wp-smush-admin.php on line 674