Merge branch '46452-nomethoderror-undefined-method-previous_changes-for-nil-nilclass' into 'master'

Resolve "NoMethodError: undefined method `previous_changes' for nil:NilClass"

Closes #46452

See merge request gitlab-org/gitlab-ce!19190

app/services/projects/update_service.rb

@@ -38,7 +38,7 @@ module Projects
     end
 
     def run_auto_devops_pipeline?
-      return false if project.repository.gitlab_ci_yml || !project.auto_devops.previous_changes.include?('enabled')
+      return false if project.repository.gitlab_ci_yml || !project.auto_devops&.previous_changes&.include?('enabled')
 
       project.auto_devops.enabled? || (project.auto_devops.enabled.nil? && Gitlab::CurrentSettings.auto_devops_enabled?)
     end

changelogs/unreleased/46452-nomethoderror-undefined-method-previous_changes-for-nil-nilclass.yml

+---
+title: Check for nil AutoDevOps when saving project CI/CD settings.
+merge_request: 19190
+author:
+type: fixed

spec/services/projects/update_service_spec.rb

@@ -275,6 +275,10 @@ describe Projects::UpdateService do
       it { is_expected.to eq(false) }
     end
 
+    context 'when auto devops is nil' do
+      it { is_expected.to eq(false) }
+    end
+
     context 'when auto devops is explicitly enabled' do
       before do
         project.create_auto_devops!(enabled: true)