Well, after installing the theme on a test site, it loaded fine with its sample content.
So I set about reloading WP and the theme on the active site. Once again, it came up fine, with no error message on the front page.
Then I started customizing the theme for my needs. As soon as I deleted the Hello World sample post – the error appeared on the front page.
It would seem there’s some code missing/needed in the theme’s WP loop to account for building a front page if there are no posts published.
My workaround: use an active post in the front page build.