I fugured out that the problem was my script editor. I used Extended Script Toolkit. Files made in EST for some reason don't run. Console shows up an error. The same code written in plain TextEdit, works just fine. How can this be that EST is no good for writing code?

Be sure to select Illustrator in the pop-up menu. EST controls every adobe-program and the commands are different for each one. You must indicate it which program will run the script.
Hope it helps.