fix: only login to docker if vars set

Author: sheldonhull

.github/workflows/release.yml

@@ -45,6 +45,7 @@ jobs:
           version: latest
           args: init
       - name: docker-login
+        if: ${{ secrets.DSV_DOCKER_USERNAME && secrets.DSV_DOCKER_PASSWORD }}
         uses: docker/login-action@9780b0c442fbb1117ed29e0efdff1e18412f7567 # v3
         with:
           username: ${{ secrets.DSV_DOCKER_USERNAME }}