Merge pull request #256 from nut-tree/feature/255/conditional_sonar

(#255) Only run sonar step if SONAR_TOKEN is set

Author: s1hofmann

.github/workflows/ci.yaml

@@ -47,6 +47,7 @@ jobs:
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}
+        if: ${{ env.SONAR_TOKEN != null }}
 
   test:
     needs: