[DRE-maint] Bug#955732: issues page of existing projects are broken with 12.8.8 update

[Pirate Praveen]

Package: gitlab
Version: 12.8.8-5+fto10+2
Severity: grave

production.log has this and the issues page gives 500.

ActionView::Template::Error (undefined local variable or method 
`attributes_changed_
by_setter' for #<Group id:13 @debian-ruby>
Did you mean? attribute_change):
    2:
    3: %aside.issues-bulk-update.js-right-sidebar.right-sidebar{ 
"aria-live" => "pol
ite", data: { 'signed-in': current_user.present? } }
    4: .issuable-sidebar.hidden
    5: = form_tag [:bulk_update, @project.namespace.becomes(Namespace), 
@project, type], method: :post, class: "bulk-update" do
    6: .block.issuable-sidebar-header
    7: .filter-item.inline.update-issues-btn.float-left
    8: = button_tag "Update all", class: "btn update-selected-issues 
btn-info", disabled: true

config/initializers/active_record_becomes.rb:22:in `becomes'
app/views/shared/issuable/_bulk_update_sidebar.html.haml:5
app/views/projects/issues/index.html.haml:16
app/controllers/application_controller.rb:122:in `render'
app/controllers/application_controller.rb:478:in `set_current_admin'
lib/gitlab/session.rb:11:in `with_session'
app/controllers/application_controller.rb:469:in `set_session_storage'