undefined method `[]' for nil:NilClass (NoMethodError)

(plugin/tlink.rb):140:in `tlink'
./tdiary.rb:72:in `join'
./tdiary.rb:72:in `safe'
./tdiary.rb:654:in `eval_src'
./tdiary.rb:901:in `do_eval_rhtml'
./tdiary.rb:851:in `eval_rhtml'
index.rb:71