chore: add validation for Docker Hub credentials in workflow

Author: nickytonline

.github/workflows/docker.yml

@@ -41,6 +41,18 @@ jobs:
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
 
+      - name: Validate Docker Hub secrets
+        run: |
+          echo "username length: ${#DOCKERHUB_USERNAME}"
+          echo "token length: ${#DOCKERHUB_TOKEN}"
+          if [ -z "$DOCKERHUB_USERNAME" ] || [ -z "$DOCKERHUB_TOKEN" ]; then
+            echo "Missing Docker credentials"
+            exit 1
+          fi
+        env:
+          DOCKERHUB_USERNAME: ${{ secrets.DOCKERHUB_USERNAME }}
+          DOCKERHUB_TOKEN: ${{ secrets.DOCKERHUB_TOKEN }}
+
       - name: Log in to Docker Hub
         uses: docker/login-action@v3
         with: