NoMethodError in Detail#show

Showing /home/kouya/main_dir/app/views/detail/show.html.erb where line #193 raised:

undefined method `+' for nil:NilClass
Extracted source (around line #103):
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#link area_pref("検索結果"), request.referer
if request.fullpath.match(/\/detail/)
link "検索結果", up_uri + '/search/result?crmb=true'
else
link "検索結果"
end

Rails.root: /home/kouya/main_dir

Application Trace | Framework Trace | Full Trace

Request

Parameters:

{"id"=>"2152", "area"=>"a2", "pref"=>"p5"}

Response

Headers:

None