fix for naigation bars independent of uinavcontroller

so i commented out your original then put my altered code. Added comments to highlight where i made changes.

Uncomment your earlier, comment mine & run to see the bug.

i don;t expect you to merge this, this is for you to see. Hopefully you'll be able to figure out why that works & refactor. It's then broken for ios6 though :(. 

let me know if you need anymore information.
I really like this scroll bar, not as complicated as others i've seen. I hope your able to figure it out.