Correcting a NPE where the user had no .minecraft whatsoever.

I saw a bug report (thankfully a stacktrace) that indicated that Arrays.sort() doesn't like empty File[]. base.listFiles() doesn't guarantee that it'll even fill the array if there's no files in the directory (for example, it doesn't exist). I've shifted the Array.sort after the check to see if files is null. I should have caught this, but I'm glad I have caught it now.

Regards, The Viking (Dr Smokey)