WP Smush Pro is Missing an Image in CSS folder

Missing image: ui-bg_glass_75_e6e6e6_1x400.png

GET http://store.soobahkdo.org/wp-content/plugins/wp-smush-pro/assets/css/images/ui-bg_glass_75_e6e6e6_1x400.png 404 (Not Found)

Checking via FTP, the specified image does not appear in the indicated folder.