Found Bug 🐛 unhandled exception: Incorrect JSON kind. Wanted '{JNull, JString}'
**Describe the bug** 🐛
hi, i try to build simple otp api with happyx, here my model

```
model MyOTP:
  email: string
  verify: string

```
on router
 ```
 post "/login/otp/verify/[m:MyOTP:json]":
    let verify = m.verify
    let email = m.email
    echo $verify

```
json data
```
{
    "email": "kugutsu.hiruko@gmail.com",
    "verify": 845944
}
```


Error: unhandled exception: Incorrect JSON kind. Wanted '{JNull, JString}' in '' but got 'JInt'. [JsonKindError]

I think it would be better for the server to respond error with 400

thanks
