mod_base: Fix controller_static_pages's rendering of template files

Regression introduced in 5f891f46e78e2854648332c44c83a344ecd47a5d.

See for description of the feature:
http://zotonic.com/docs/0.9/ref/controllers/controller_static_pages.html
(cherry picked from commit 3f28a4aa919ee31f46922ef4662c20e81e6e63fd)