undefined method `add_comment' for nil:NilClass (NoMethodError)

/usr/local/tdiary/tdiary/defaultio.rb:41:in `restore_comment'
/usr/local/tdiary/tdiary/defaultio.rb:32:in `each'
/usr/local/tdiary/tdiary/defaultio.rb:32:in `restore_comment'
/usr/local/tdiary/tdiary/defaultio.rb:30:in `open'
/usr/local/tdiary/tdiary/defaultio.rb:30:in `restore_comment'
/usr/local/tdiary/tdiary/defaultio.rb:137:in `transaction'
/usr/local/tdiary/tdiary.rb:1697:in `initialize'
/home/sites/www.kankanbou.com/web/kankan/kissa/index.rb:46:in `new'
/home/sites/www.kankanbou.com/web/kankan/kissa/index.rb:46