Generate HTTP URLs for custom Pages domains when appropriate

app/models/pages_domain.rb

@@ -27,7 +27,7 @@ class PagesDomain < ActiveRecord::Base
   def url
     return unless domain
 
-    if certificate
+    if certificate.present?
       "https://#{domain}"
     else
       "http://#{domain}"

changelogs/unreleased/28260-fix-pages-custom-domain-url.yml

+---
+title: Generate HTTP URLs for custom Pages domains when appropriate
+merge_request: 16279
+author:
+type: fixed

spec/models/pages_domain_spec.rb

@@ -68,7 +68,7 @@ describe PagesDomain do
     subject { domain.url }
 
     context 'without the certificate' do
-      let(:domain) { build(:pages_domain) }
+      let(:domain) { build(:pages_domain, certificate: '') }
 
       it { is_expected.to eq('http://my.domain.com') }
     end