It seems there is a inheritance error in the midi handling tutorial with the note off function. The fix is easy. Just add velocity as parameter so it matches the parameter set in the api version of the funtion.
Also I'm new here and I just wanted to say that learning audio unit developement with juce is one millions.0 times better and easier than using the mostly broken and out date documentation apple provides. Seriously I wasted months tracking down error in their example code just getting it into a compilable form so I could see how it worked. All I have to say is thanks to the JUCE team for making the process so much more painless.