cloudron-setup: check if box.service exists instead

scripts/cloudron-setup

@@ -41,7 +41,8 @@ if [[ "${disk_size_gb}" -lt "${MINIMUM_DISK_SIZE_GB}" ]]; then
     exit 1
 fi
 
-if systemctl -q is-active box; then
+# do not use is-active in case box service is down and user attempts to re-install
+if systemctl cat box.service 2>/dev/null; then
     echo "Error: Cloudron is already installed. To reinstall, start afresh"
     exit 1
 fi