Warning: Invalid argument in WP Smush

I'm receiving this error with WP Smush Pro after smushed all the images and when I check all the images in media library I see the error under WP Smush:

Warning: Invalid argument supplied for foreach() in /home/allergypartners/public_html/wp-content/plugins/wp-smush-pro/lib/class-wp-smush.php on line 1469
Reduced by 31.92 KB ( 6.4% )