Merge branch 'rails5-fix-47835' into 'master'

Rails5 fix no implicit conversion of Hash into String

Closes #47835

See merge request gitlab-org/gitlab-ce!19792

changelogs/unreleased/rails5-fix-47835.yml

+---
+title: Rails5 fix no implicit conversion of Hash into String. ActionController::Parameters
+  no longer returns an hash in Rails 5
+merge_request: 19792
+author: Jasper Maes
+type: fixed

lib/api/helpers.rb

@@ -272,7 +272,8 @@ module API
           attrs[key] = params_hash[key]
         end
       end
-      ActionController::Parameters.new(attrs).permit!
+      permitted_attrs = ActionController::Parameters.new(attrs).permit!
+      Gitlab.rails5? ? permitted_attrs.to_h : permitted_attrs
     end
 
     def filter_by_iid(items, iid)