[Plugin: Cleaner Gallery] Problem with my HTTPS secure pages when using C.G.

I’m using the Cleaner Gallery on my WordPress site that also uses the Shopp e-commerce plugin.

When the user is brought to the checkout page, which has an address beginning with ‘https://’ the browser shows the “Connection Partially Encrypted’ error. The error continues, “Parts of the page you are viewing were not encrypted before being transmitted over the Internet.”

I investigated and noticed that the CSS file for the Cleaner Gallery is included with an absolute URL that does not begin with ‘https://’ like the rest of the associated files for various plugins. Instead it begins with ‘http://’

I deactivated the plugin and reloaded the checkout page, and the security warning disappeared.

Has anybody else seen this. Can you recommend a revision that I can make to the plugin to prevent this?

Thank you,
Adam