allow 0 sources, uglifyjs does that when a file contains no real code (eg only comments)
allow 0 sources, uglifyjs does that when a file contains no real code (eg only comments)

koala-framework/koala-framework,yacon/koala-framework,nsams/koala-framework,kaufmo/koala-framework,yacon/koala-framework,nsams/koala-framework,yacon/koala-framework,kaufmo/koala-framework,nsams/koala-framework,kaufmo/koala-framework,koala-framework/koala-framework