Asset processing with Grunt lib.js not exits

[u.wang]

all.json lists JavaScript files to process into lib.js.

But after run the grunt build

Running "uglify:lib" (uglify) task
>> Destination web/js/lib.min.js not written because src files were empty.
>> No files created.

web/js/lib.js not exits

I'm not sure if I'm mistaken, or web/js/lib.js missing in the Gruntfile.js 😟