Multilanguage first page issue

With this theme I can't setup different first page per language.
I've tried all method reported in this post with no success.
The first page loaded wasn't related to actual language but it was related to default site language.
I've identified the problem in the method used to link first page base_path. I don't know if this is the best practise but I've changed base_path() in check_url($front_page) and all seems to work.