undefined method `+' for Hash: git-rank.rb:16:in `each'

[kadishmal]

The following error has occurred when I tried to run git rank.

$ git rank --author "Author Name"
warning: only found copies from modified paths due to too many files.
warning: you may want to set your diff.renamelimit variable to at least 5073 and retry the command.
/usr/lib/ruby/vendor_ruby/1.8/rubygems/custom_require.rb:36:in `inject': undefined method `+' for {:additions=>39, :deletions=>18, :net=>21, :total=>57}:Hash (NoMethodError)
    from /var/lib/gems/1.8/gems/git-rank-0.0.1/lib/git-rank.rb:16:in `each'
    from /var/lib/gems/1.8/gems/git-rank-0.0.1/lib/git-rank.rb:16:in `inject'
    from /var/lib/gems/1.8/gems/git-rank-0.0.1/lib/git-rank.rb:16:in `sum'
    from /var/lib/gems/1.8/gems/git-rank-0.0.1/lib/git-rank/printer.rb:11:in `print'
    from /var/lib/gems/1.8/gems/git-rank-0.0.1/lib/git-rank/printer.rb:10:in `each'
    from /var/lib/gems/1.8/gems/git-rank-0.0.1/lib/git-rank/printer.rb:10:in `print'
    from /var/lib/gems/1.8/gems/git-rank-0.0.1/bin/git-rank:9
    from /usr/local/bin/git-rank:19:in `load'
    from /usr/local/bin/git-rank:19