Fix grunt-autoprefixer blocking grunt when it finds no files

[0xR]

Fixes #115

[nDmitry]

Thanks but I already fixed this, so closing this one.

[0xR]

Yeah about that, it isn't fix. Your new code still assumes this.files is not empty. When it is empty the forEach loop is never called and done() is never called. My fix does fix it.

[nDmitry]

With what exactly config this.files can be empty?

I'm running grunt-autoprefixer with src property that maps nothing and get the following:

$ grunt autoprefixer
Running "autoprefixer:dist" (autoprefixer) task
>> No source files were found.

Done, without errors.

[0xR]

    autoprefixer: {
      options: {
        browsers: ['> 5%', 'last 2 version', 'ie >= 9']
      },
      dist: {
        files: [
          {
            expand: true,
            cwd: '.tmp/css/',
            src: '**/*.css',
            dest: '.tmp/css/'
          }
        ]
      }
    },

[nDmitry]

Ok, let's add this condition too.

[nDmitry]

Thanks for the help!