fix: support of empty ``docker-compose`` struct in compose YAML

bin/compose-core

@@ -840,9 +840,8 @@ _get_docker_compose_opts() {
 
     compose_def="$(get_compose_service_def "$service")" || return 1
     master_service="$(get_top_master_service_for_service "$service")"
-    docker_compose_opts=$(echo "$compose_def" | shyaml get-value "docker-compose" 2>/dev/null)
 
-    if [ "$docker_compose_opts" ]; then
+    if docker_compose_opts=$(echo "$compose_def" | shyaml get-value -y "docker-compose" 2>/dev/null); then
         yaml_key_val_str "$master_service" "$docker_compose_opts"
     fi | tee "$cache_file"
     if [ "${PIPESTATUS[0]}" != 0 ]; then