Well, Barron's code is right.
That code is supposed to prevent the user from using other than the "internal" (1st person) view, by permanently forcing it. Therefore, you can no longer use "gunner", "external" or "group" views.
The same will happen if you disable the external view through the options menu.
Sorry, mate, but there haven't been found any solutions to this, at least that I know.
You could try adding a menu action that switches from "external" to "gunner" view and vice-versa. Anyway, it will be kind of odd to use...