Handle status properly if container is not installed

root/usr/libexec/apps/btcpayserver/btcpayserver.sh

@@ -101,7 +101,11 @@ case "${ACTION}" in
   "status")
     APP_NAME="btcpayserver"
     CONTAINER_NAMES=$(docker ps -a --filter "name=${APP_NAME}" --format '{{.Names}}')
-    docker ps --all -f "name=${CONTAINER_NAMES}" --format '{{.Status}}'
+    if [ -z "$CONTAINER_NAMES" ]; then
+        echo "${APP_NAME} is not installed."
+    else
+        docker ps --all -f "name=${CONTAINER_NAMES}" --format '{{.Status}}'
+    fi
     ;;
   "port")
     APP_NAME="btcpayserver"