gen: allOf and nullable generate broken code

[WinPooh32]

What version of ogen are you using?

Latest commit at the main branch:
go run github.com/ogen-go/ogen/cmd/ogen@a794ac8

Can this issue be reproduced with the latest version?

Yes

What did you do?

I am trying to add nullable property using allOf:

            schema:
              type: object
              properties:
                field_1: # this field causes issues.
                  allOf:
                    - $ref: "#/components/schemas/dateTime"
                    - nullable: true

Full openapi.yaml:

openapi: 3.0.2
servers:
  - url: http://localhost:8000/api/v1
info:
  version: 1.0.0
  title: issue example
paths:
  /example:
    patch:
      requestBody:
        required: true
        content:
          "application/json":
            schema:
              type: object
              properties:
                field_1: # this field causes issues.
                  allOf:
                    - $ref: "#/components/schemas/dateTime"
                    - nullable: true
                field_2:
                  type: string
                  nullable: true
                field_3: # reference field without issues.
                  type: string
      responses:
        "200":
          description: "OK"
components:
  schemas:
    dateTime:
      type: string
      format: date-time
      description: |
        Date and Time
        [RFC3339](https://www.rfc-editor.org/rfc/rfc3339)
      example: "2006-01-02T15:04:05Z07:00"

What did you expect to see?

No compilation errors and nullable field.

What did you see instead?

$ go run github.com/ogen-go/ogen/cmd/ogen@a794ac8 -v --clean --config generate_config.yaml --target . -package example openapi.yaml
$ go build .
# ogenissue
./oas_json_gen.go:25:20: not enough arguments in call to s.Field1.Encode
        have (*jx.Encoder)
        want (*jx.Encoder, func(*jx.Encoder, time.Time))

Full example of the issue available here: https://github.com/WinPooh32/ogenissue