warning when running blog.sh

[clacote]

➜  blog git:(post/happy-new-year) ./blog.sh 
/usr/local/lib/ruby/gems/2.2.0/gems/liquid-2.6.1/lib/liquid/htmltags.rb:43: warning: duplicated key at line 46 ignored: "index0"
Configuration file: /Users/sryl/workspace/ninja/blog/_config.yml
            Source: /Users/sryl/workspace/ninja/blog
       Destination: /Users/sryl/workspace/ninja/blog/_site
      Generating... 
                    done.
 Auto-regeneration: enabled for '/Users/sryl/workspace/ninja/blog'
Configuration file: /Users/sryl/workspace/ninja/blog/_config.yml
    Server address: http://0.0.0.0:4000/
  Server running... press ctrl-c to stop.