Fix non-HTML requests with vue_issues_list

This fixes a regression from
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/79408

We still need to query the issues for the ATOM feed even if
vue_issues_list is enabled

app/controllers/groups_controller.rb

@@ -210,7 +210,7 @@ class GroupsController < Groups::ApplicationController
   end
 
   def issues
-    return super if Feature.disabled?(:vue_issues_list, group, default_enabled: :yaml)
+    return super if !html_request? || Feature.disabled?(:vue_issues_list, group, default_enabled: :yaml)
 
     @has_issues = IssuesFinder.new(current_user, group_id: group.id).execute
       .non_archived
@@ -220,7 +220,6 @@ class GroupsController < Groups::ApplicationController
 
     respond_to do |format|
       format.html
-      format.atom { render layout: 'xml.atom' }
     end
   end
 

app/controllers/projects/issues_controller.rb

@@ -22,10 +22,7 @@ class Projects::IssuesController < Projects::ApplicationController
   before_action :issue, unless: ->(c) { ISSUES_EXCEPT_ACTIONS.include?(c.action_name.to_sym) }
   after_action :log_issue_show, unless: ->(c) { ISSUES_EXCEPT_ACTIONS.include?(c.action_name.to_sym) }
 
-  before_action :set_issuables_index, if: ->(c) {
-    SET_ISSUABLES_INDEX_ONLY_ACTIONS.include?(c.action_name.to_sym) ||
-    (c.action_name.to_sym == :index && Feature.disabled?(:vue_issues_list, project&.group, default_enabled: :yaml))
-  }
+  before_action :set_issuables_index, if: ->(c) { SET_ISSUABLES_INDEX_ONLY_ACTIONS.include?(c.action_name.to_sym) }
 
   # Allow write(create) issue
   before_action :authorize_create_issue!, only: [:new, :create]
@@ -80,6 +77,8 @@ class Projects::IssuesController < Projects::ApplicationController
   attr_accessor :vulnerability_id
 
   def index
+    set_issuables_index if !html_request? || Feature.disabled?(:vue_issues_list, project&.group, default_enabled: :yaml)
+
     @issues = @issuables
 
     respond_to do |format|