Duplicated checkboxes to show dependent colours on sub-theme settings

In GovCMS SaaS, after creating a sub-theme, it sometimes shows duplicated checkboxes for dependent colours.

Steps to reproduce

1. Install GovCMS SaaS
2. Install CivicTheme by copying the latest dev release into `themes/custom/civictheme`
3. Create a sub-theme in the sibling directory to `themes/custom/civictheme`
4. Login to the site, navigate to the Sub-theme settings page and observe the duplicated checkboxes