Update ci.yml

Author: Merlin Rabens

.github/workflows/ci.yml

@@ -28,4 +28,4 @@ jobs:
         with: 
           status: ${{ job.status }}
           steps: ${{ toJson(steps) }}
-        if: secrets.SLACK_WEBHOOK_URL && failure()
+        if: ${{ secrets.SLACK_WEBHOOK_URL }} && failure()