Spinner.gif and ‘Mixed Content’

Seems the call to load the spinner.gif is done over http. The produces notices in the javascript panel about mixed content: Mixed Content: The page at ‘https://mywebsite.com/’ was loaded over HTTPS, but requested an insecure image ‘https://mywebsite.com/wp-content/plugins/mailoptin/vendor/mailoptin/core/src/assets/images/spinner.gif’. This content should also be served over HTTPS.

For some weird reason, we got users who use our complaining about security because of this. If you have a git or a repo someplace, I’d be happy to take a look at it and fix it. ??