Fix for %s shown instead of a file list

It seems that not everything went OK about 9 months ago while preparing the program for translation. When applying transformations on a subset of the visible files the confirmation asked about a "%s" instead of showing details about the file list. Well, now it's fixed and it looks like it's the only error of this kind. If you work with subsets of files, you can download the latest version (1.1.21) to take care of this.