Subscription alert matching error: Missing parameter "json"

[liuxin638507]

Question and Steps to reproduce

这条告警就会失败
测试通知已发送，通知目标返回响应如下：
{"errcode":40035,"errmsg":"缺少参数 json"}

具体告警事件
nightingale_prometheus
/
model模型健康检测失败
name=service_health
error_msg={"code":5001,"error":"HTTP 402 Payment Required;{"error":{"message":"This request requires more credits, or fewer max_tokens. You requested up to 20 tokens, but can only afford 2. To increase, visit https://openrouter.ai/settings/keys and create a key with a higher total limit","code":402,"metadata":{"provider_name":null}},"user_id":"user_31awZgKFvtxYDjQ8uNbCsyF9nZL"}"}
ident=10.8.28.105
instance=aaas-shengchan-10.8.28.143:30002
rulename=model模型健康检测失败
service_name=google/gemini-2.5-pro

但是下面这条又能告警
告警事件内容：
nightingale_prometheus
/
视频流监测异常
name=service_health
error_msg=curl: (28) Operation timed out after 5002 milliseconds with 0 bytes received HTTP_CODE:000
ident=172.16.36.60
instance=大屏服务器
rulename=视频流监测异常

即使上面报错的哪条在告警规则（不是订阅规则）里通过告警接收组的形式又能收到告警。就是订阅规则里面不行，感觉是订阅规则对error_msg处理转换成json的时候有问题，

Relevant logs and configurations

测试通知已发送，通知目标返回响应如下：
{"errcode":40035,"errmsg":"缺少参数 json"}

Version

n9e v8.4.1