fix undefined

docs/container_deploy_request.md

@@ -585,7 +585,7 @@ HTTP handler 最多等待 10 秒。超时返回 HTTP 504，其他参数或执行
                 <<"working_dir">> => <<>>,
                 <<"hostname">> => <<>>,
                 <<"exposed_ports">> => [],
-                <<"healthcheck">> => <<"__undefined__">>
+                <<"healthcheck">> => undefined
             },
             <<"host_config">> => #{
                 <<"binds">> => [],

src/transport/tcp/ssl_channel.erl

@@ -317,7 +317,7 @@ safe_term(true) ->
 safe_term(false) ->
     false;
 safe_term(undefined) ->
-    <<"__undefined__">>;
+    undefined;
 safe_term(Value) when is_atom(Value) ->
     atom_to_binary(Value, utf8);
 safe_term(Value) when is_map(Value) ->