fix: provide a sensible help when using ``run`` command without any services.

bin/compose-core

@@ -3800,7 +3800,7 @@ if [ "$full_init" ]; then
 
 fi
 
-if [ "$action" == "run" ]; then
+if [ "$action" == "run" -a "${#services_args}" != 0 ]; then
     charm=$(get_service_charm "${services_args[0]}") || exit 1
     metadata=$(charm.metadata "$charm") || exit 1
     type="$(printf "%s" "$metadata" | shyaml get-value type 2>/dev/null)" || true