`TCommentBlock` does not replace substrings defined in `replacements` option when block gets commented if `middle` option is left empty. The issue gets away without any apparent damage when [this `if` condition](https://github.com/tomtom/tcomment_vim/blob/260680593fb643693e53e1ec46920ffa3bf6cffb/autoload/tcomment.vim#L871) is removed.