I had the same problem before and after a lot of trials the problem was in the controller name spelling and case. For example (based on your question code) calling:
MovieTracker.moviesController.get('length');
while the name of the controller is MoviesController with a capital M will give you this error. So try double checking your code, make sure you have the correct name with correct case.
It is also a good practice to keep controller name with capital M as @kingpin2k recommended