Forum thread controller change only.

This alpha_numeric was causing the issue for the script on the views page forum/create.

Old

-  $this->form_validation->set_rules('thread-slug', 'lang:forums_slug', 'required|trim|xss_clean|alpha_numeric|is_unique[forums_threads.slug]');

New

+  $this->form_validation->set_rules('thread-slug', 'lang:forums_slug', 'required|trim|xss_clean|is_unique[forums_threads.slug]');