Fix: hide `archives` in sidebar if equal to 0.
Fix: hide `archives` in sidebar if equal to 0.

If in main config of hexo `archive_dir` is set to '/' then archives will not generate by hexo-generator-archive: https://github.com/hexojs/hexo-generator-archive/blob/master/lib/generator.js#L19

Idea take from #639.
mchsinx/hexo-theme-next