This section of code, I understand why you wrote this, but unfortunately, in 6 months time this is going to be unintuitive to us both as well as to any future maintainers. 

Back-story: The only two screens that have only a "Back" button are the TOS and PP. Neither of these screens contain scripts. @OlavHN is using the lack of scripts as a proxy indicator to signal that the screen has only a back button.

I think we should try to use an explicit signal, either a data-attribute on the screen's DOM or by adding basic scripts to each of these screens that hook up the `.left` button.