Don't start production instances if backend folder doesn't exist

production/mempool-start-all

@@ -3,6 +3,6 @@ export NVM_DIR="$HOME/.nvm"
 source "$NVM_DIR/nvm.sh"
 for site in mainnet liquid testnet bisq signet
 do
-    cd "${HOME}/${site}/backend/"
+    cd "${HOME}/${site}/backend/" && \
     screen -dmS "${site}" sh -c 'while true;do npm run start-production;sleep 1;done'
 done