ofVideoGrabber and ofThread crash on exit (osx)

Having an ofThread and ofVideoGrabber, and trying to close the thread nicely waiting for its work getting done when exiting, makes the videograbber to crash on exit with a EXC_BAD_ACCESS in libsystem_kernel.dylib. I can see the crash is related to [QTKitVideoGrabber stop]

#include "ofApp.h"
void ofApp::setup(){
    startThread();
    grabber.setup(600,400);
}

void ofApp::update(){
    grabber.update();
}

void ofApp::draw(){
    grabber.draw(0,0);
}

void ofApp::exit(){
    if(isThreadRunning()){
        waitForThread();
    }
}

void ofApp::threadedFunction(){
    while(isThreadRunning()) {
        sleep(5);
    }
}

If i leave out sleep(5), then there is no problem.

Running on OSX 10.11.2

Reproduce the provided ofThread and ofVideoGrabber example on OSX 10.11.2, focusing on the exit path and the QTKitVideoGrabber stop call. Compare behavior with and without sleep(5), then trace the thread shutdown and video-grabber cleanup. Done means the example exits without the EXC_BAD_ACCESS crash while waiting for the thread to finish.