Oh, don't worry about it, I totally get where you're coming from. >_>
The app is called "Tumblr Savior". It's a fantastic thing to have around.
I also recommend Xkit, while you're at it -- it's another free app that makes Tumblr a lot more customizable, basically giving you all the features that you can't believe don't already exist. (...And also, there's a game where you can catch Pokemon that randomly generate on your dashboard as you scroll. Fun stuff.)
Edit: Oh, just be sure you get "new xkit". The old one isn't supported anymore as its developer sort of abandoned the internet. o_o