overlay.png 404 error

Based on https://tribulant.com/forums/discussion/2100/overlay-png-is-incorrectly-referenced-in-the-views-default-css-colorbox-css-file it seems like this problem has been around since September 2015.

My difficulty is that I need to do some debugging on my site and this is getting in the way. I’d rather not start editing / patching plugin files if possible.

Is this a difficult one to resolve?