Fix Auto DevOps check domain is blank

changelogs/unreleased/57798-fix-auto-devops-empty-str-check.yml

+---
+title: Prevent Auto DevOps from trying to deploy without a domain name
+merge_request: 25308
+author:
+type: fixed

lib/gitlab/ci/templates/Auto-DevOps.gitlab-ci.yml

@@ -828,7 +828,7 @@ rollout 100%:
 
   # Function to ensure backwards compatibility with AUTO_DEVOPS_DOMAIN
   function ensure_kube_ingress_base_domain() {
-    if [ -z ${KUBE_INGRESS_BASE_DOMAIN+x} ]; then
+    if [ -z ${KUBE_INGRESS_BASE_DOMAIN+x} ] && [ -n "$AUTO_DEVOPS_DOMAIN" ] ; then
       export KUBE_INGRESS_BASE_DOMAIN=$AUTO_DEVOPS_DOMAIN
     fi
   }