Fix render :text => false and render :text => nil

Obie Fernandez (http://www.jroller.com/obie/entry/render_text_gotcha)
was asking in the #rails-contrib channel about getting this ticket
(http://dev.rubyonrails.org/ticket/6684) fixed. If someone's free
could you please review/verify it and appease the "ignored" ticket
reporter ;)?

Cheers,
Chu Yeow

+1 looks like a smart, easy fix (Disclaimer: I haven't applied the patch myself)