fix: enhance Gitea registry login step to handle empty secrets

.gitea/workflows/build.yml

@@ -27,7 +27,21 @@ jobs:
         run: docker build -t condado-newsletter:latest -f Dockerfile.allinone .
 
       - name: Log in to Gitea container registry
-        run: echo "${{ secrets.REGISTRY_PASSWORD }}" | docker login ${REGISTRY} -u "${{ secrets.REGISTRY_USERNAME }}" --password-stdin
+        run: |
+          REGISTRY_USERNAME="${{ secrets.REGISTRY_USERNAME }}"
+          REGISTRY_PASSWORD="${{ secrets.REGISTRY_PASSWORD }}"
+
+          if [ -z "$REGISTRY_USERNAME" ]; then
+            REGISTRY_USERNAME="${{ github.actor }}"
+            echo "REGISTRY_USERNAME secret is empty; falling back to github.actor: $REGISTRY_USERNAME"
+          fi
+
+          if [ -z "$REGISTRY_PASSWORD" ]; then
+            echo "REGISTRY_PASSWORD secret is empty; cannot log in to ${REGISTRY}."
+            exit 1
+          fi
+
+          echo "$REGISTRY_PASSWORD" | docker login ${REGISTRY} -u "$REGISTRY_USERNAME" --password-stdin
 
       - name: Tag registry images
         run: |