UltCombo/gulp-buster — pull request #4 by mathisonian (2014-04-15 19:49:26+00:00)
Title: fix when passed fileset is empty

Current behavior causes a crash in the case that buster is given an empty set of files,

e.g.
```js
return gulp
.src('doesnt/match/anything/**/*')
.pipe(bust('mypath'))
.pipe( gulp.dest('.') );
```

this patch adds a check for undefined that prevents this.