Update ci.yml

.github/workflows/ci.yml

@@ -215,6 +215,11 @@ jobs:
         with:
           bundler-cache: true
           ruby-version: ${{ matrix.ruby }}
+      - name: Create empty Gemfile if not exists
+        run: |
+          if [ ! -f Gemfile ]; then
+            echo "source 'https://rubygems.org'" > Gemfile
+          fi
       - name: Generate binstubs
         run: bundle binstubs bundler-audit brakeman rubocop
       # Add or replace any other lints here