don't try to download VAPID keys if KV doesn't exists

.github/workflows/deploy.yml

@@ -125,6 +125,7 @@ jobs:
         env:
           CLOUDFLARE_ACCOUNT_ID: ${{ secrets.CF_ACCOUNT_ID }}
         continue-on-error: true
+        if: ${{ env.tfstate_kv != '' }}
 
       - name: generate VAPID keys if needed
         run: |