I installed a new cabin filter in my 2013 Versa S (the slot was empty so apparently the factory didn't include one). It was easy to find and install, but the filter included a piece a plastic that juts out, preventing me from putting the little removable door back on. Forgive me for calling it a a "little removable door," but I don't know the real term. You know what I mean; the piece of plastic that pops off to reveal the slit where the filter will slide in. The filter seems to fit fine without it. Do I need to put that thing back on for the filter to remain safely in place?