Stack overflow in regexp matcher: /^(.{50}).*$/i (RegexpError)

/home/esk/html_gamekei/diary/tdiary.rb:792:in `disp_referer'
/home/esk/html_gamekei/diary/tdiary.rb:72:in `join'
/home/esk/html_gamekei/diary/tdiary.rb:72:in `safe'
/home/esk/html_gamekei/diary/tdiary.rb:654:in `eval_src'
/home/esk/html_gamekei/diary/tdiary.rb:901:in `do_eval_rhtml'
/home/esk/html_gamekei/diary/tdiary.rb:851:in `eval_rhtml'
/home/esk/html_gamekei/diary/index.rb:71