XCode SDL app crashes after main loop

I compiled my SDL app using XCode, and when 开发者_如何学GoI "Build & Run", it works fine. But when I click on the .app file outside of XCode, the application crashes after I click the "Start" button.

I've included the images, sounds, and font in the same folder as my .app, but is there anything else that I need to put in that folder? I am using SDL_image, SDL_ttf, and SDL_mixer.