NoMethodError in Companyprofile::Home#pages

Showing /home/deploy/ciracas-compro/app/views/companyprofile/home/pages.html.erb where line #4 raised:

undefined method `+' for nil:NilClass
Extracted source (around line #4):
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<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta/css/bootstrap.min.css">
</head> -->
<% content_for :title, @title_header + '-' + 'RSUD Ciracas'%>
<style>
section {
padding: 50px 0;

Rails.root: /home/deploy/ciracas-compro

Application Trace | Framework Trace | Full Trace

Request

Parameters:

{"key"=>"pages", "slug"=>"petugas-keamanan-31"}

Response

Headers:

None