ci(earthly): Make docker login optional

images/.utils/gitlab-earthly.yaml

@@ -14,6 +14,11 @@
       - earthly config global.disable_log_sharing true
       - earthly account logout
       - earthly bootstrap
-      - docker login -u $CI_REGISTRY_USER -p $CI_REGISTRY_PASSWORD $CI_REGISTRY
+      - |
+        if [ -n "$CI_REGISTRY" ] && [ -n "$CI_REGISTRY_USER" ] && [ -n "$CI_REGISTRY_PASSWORD" ]; then
+          docker login -u $CI_REGISTRY_USER -p $CI_REGISTRY_PASSWORD $CI_REGISTRY
+        else
+          echo "Missing variable. Skipping docker login!"
+        fi
   tags:
     - privileged
\ No newline at end of file