Error while running edgeChns.m

[zhuzihao-hz]

Hi!
Thanks pdollar for this excellent work. I'm trying to run edgesDemo.m, before that, I install it as Installation in readme.txt.
But when the program running to the 25 line in edgesDemo.m, it call the edgesDetect.m, and then edgesDetect call the edgesChns.m, in 58 lines in edgesChns.m, it call gradientMag.cpp, and Matlab was down. I have tried several times and it is same.
Help!

The environment I use:
Mac OS Mojave 10.14 5
Matlab 2017
Xcode Clang++ to configure mex