fix: only do a Docker Login if the secrets are available

Author: Sam Harrison

.github/workflows/test-and-deploy.yml

@@ -20,6 +20,7 @@ jobs:
         ruby: [ '2.4', '2.5', '2.6', '2.7', '3.0', jruby-9.2 ]
     env:
       version: ${{ format('ruby:{0}', matrix.ruby) }}
+      DOCKER_LOGIN: ${{ secrets.DOCKER_USERNAME && secrets.DOCKER_AUTH_TOKEN }}
     steps:
       - name: Revise env version if necessary
         run: echo "version=jruby:9.2" >> $GITHUB_ENV
@@ -30,18 +31,19 @@ jobs:
         with:
           fetch-depth: 0
 
-      - name: Set up Ruby
-        uses: ruby/setup-ruby@v1
-        with:
-          ruby-version: ${{ matrix.ruby }}
-          bundler-cache: true
-
       - name: Login to Docker Hub
+        if: env.DOCKER_LOGIN
         uses: docker/login-action@v1
         with:
           username: ${{ secrets.DOCKER_USERNAME }}
           password: ${{ secrets.DOCKER_AUTH_TOKEN }}
 
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby }}
+          bundler-cache: true
+
       - run: make install
 
       - name: Set up linter