it seems like the iconset should be imageset

[IanLuo]

otherwise the icon won't work properly, the image has 3 sizes (1x, 2x, 3x) apparently should be for image not appicon, in iconset will ask you to assign other sizes, that for the app icon I guess.

I modified the code by changing the dir name from *.iconset to *.imageset, which works fine for me, maybe you should change that.