Failed to load plugin url: …

I just updated to 4.9 and I am getting this error when I open up a custom post created by Testimonial Rotator Plugin.

Failed to load plugin url: https://montanashedcenter.com/wp-content/plugins/ninja-tables/assets/js/ninja-table-tinymce-button.js

I am not sure if it is your plugin or something with Testimonial Rotator Plugin. Funny thing is I can’t find this js in your assets folder.