500 Internal Server Error

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

./tdiary/defaultio.rb:92:in `restore_referer'
./tdiary/defaultio.rb:89:in `each'
./tdiary/defaultio.rb:89:in `restore_referer'
./tdiary/defaultio.rb:86:in `each'
./tdiary/defaultio.rb:86:in `restore_referer'
./tdiary/defaultio.rb:84:in `open'
./tdiary/defaultio.rb:84:in `restore_referer'
./tdiary/defaultio.rb:155:in `transaction'
./tdiary.rb:1873:in `initialize'
index.rb:52:in `new'
index.rb:52