The sourcemap conusmer leaves empty comments in the file

[Lexicality]

concatting pre-processed files work, but the comments that used to hold the sourcemap line are not removed.

        concat:
            two:
                src: [
                    'a.min.js'
                    'b.min.js'
                ]
                dest: 'stubs.js'
            options:
                sourceMap: true
                sourceMapStyle: 'embed'
        uglify:
            one:
                src: [
                    'a.js'
                    'b.js'
                ]
                dest: '.'
                ext: '.min.js'
                expand: true
            options:
                sourceMap: true
                sourceMapIncludeSources: true
                sourceMapRoot: ''

results in

var Hogan={};!function(a,b){function c(a)// . . .
//
!function(a){function b(a){"}"===a.n.subs// . . .
//
//# sourceMappingURL=stubs.js.map

for the sake of having it somewhere I added this to the demonstratror from #131, https://github.com/Lexicality/grunt-concat-sourcemap-issue
Just run grunt stubs instead of grunt.