It doesn't work when input argument is null

### What happened?

**The input schema**

```
extend type Query {
apiResponse(id: ID!,filter:MakerFilterInput): Any
}
```

** when run the query**

query httpresp {
apiResponse(id:"xxxx") // The arg "filter" is null, get the error: but if the filter is not null.it works well
}

**error**:

```

{
"errors": [
{
"message": "internal system error",
"path": [
"apiResponse"
]
}
],
"data": {
"apiResponse": null
}
}
```

### What did you expect?

### Minimal graphql.schema and models to reproduce

### versions
- `go run github.com/99designs/gqlgen version`? v0.17.14
- `go version`? 1.18