Overwriting css in-place fails silently

[Kilian]

With the command cssbeautify-cli -f style.css -w style.css I expect the file to beautify in-place but this it not what happens. It ends up with a one-line file:

/**** style.css ***/

Obviously this is not what I want. I think that cssbeautify-cli should either support this behavior, or give a warning/prevent users from doing this.