In short, try this:
- Switch from http to https on both variables in your wordpress configuration
- Install the WP-Less plugin. It's a more recent version than the version that is delivered with Touchfolio. That threw me another error about a not defined variable: @menu-font-color (E.g. @menu-font-color: #999;)
So I defined it in style-touchfolio-default.less an voilá, my site is available via https and http
Long story: I recently installed the old Touchfolio theme for Wordpress and ran into one problem. The site was only available without SSL. After two days I told wordpress to be accessible via https set the two URL variables. Now the site was accessible via SSL, BUT http didn't work anymore. The result was the same white screen as before the change. So I dug into it deeper, turned debug on and found out there was some problem with the lesscompiler (whatever that is ...) and googled the error message to find out there is a WP-Less plugin. So I installed it and after another error message (above) I finally solved my problem and it saved me three days of polishing the theme to my liking. Pew!
I hope that little blog entry might help someone someday!