Admin page resources blocked on secure/HTTPS site

Chrome is blocking a resource on the plugin’s settings pages, which is supposed to display an ad for Worp Drive in the admin page sidebar.

The blocked resource is:

http://www.icontrolwp.com/custom/remote/plugins/hlt-bootstrapcss-plugin-widgets.php?page=icwp-wptb-bootstrapcss&snippet=side-widgets-wtb

It should be loaded using HTTPS or a protocol-relative URL.