handle nullable in allOf

[zhuscat]

Steps to reproduce

I have a swagger schema like this:

...
                    "coverImage": {
                        "allOf": [
                            {
                                "$ref": "#/components/schemas/DisplayImage"
                            },
                            {
                                "nullable": true
                            }
                        ]
                    }
...

Expected results

DisplayImage? coverImage

Actual results

dynamic coverImage

Your OpenApi snippet

{
    "info": {
        "title": "An API",
        "version": "v1"
    },
    "openapi": "3.0.0",
    "components": {
        "schemas": {
            "DisplayImage": {
                "type": "object",
                "properties": {
                    "uri": {
                        "type": "string"
                    },
                    "width": {
                        "type": "integer",
                        "nullable": true
                    },
                    "height": {
                        "type": "integer",
                        "nullable": true
                    },
                    "blurhash": {
                        "type": "string",
                        "nullable": true
                    },
                    "displayUrl": {
                        "type": "string"
                    }
                },
                "required": [
                    "uri",
                    "displayUrl"
                ]
            },
            "Test1Response": {
                "type": "object",
                "properties": {
                    "coverImage": {
                        "$ref": "#/components/schemas/DisplayImage"
                    },
                    "message": {
                        "type": "string"
                    }
                },
                "required": [
                    "coverImage",
                    "message"
                ]
            }
        },
        "parameters": {}
    },
    "paths": {
        "/test/test1": {
            "get": {
                "responses": {
                    "200": {
                        "content": {
                            "application/json": {
                                "schema": {
                                    "$ref": "#/components/schemas/Test1Response"
                                }
                            }
                        }
                    }
                }
            }
        },
        "/test/test2": {
            "get": {
                "responses": {
                    "200": {
                        "content": {
                            "application/json": {
                                "schema": {
                                    "allOf": [
                                        {
                                            "$ref": "#/components/schemas/Test1Response"
                                        },
                                        {
                                            "properties": {
                                                "coverImage": {
                                                    "allOf": [
                                                        {
                                                            "$ref": "#/components/schemas/DisplayImage"
                                                        },
                                                        {
                                                            "nullable": true
                                                        }
                                                    ]
                                                },
                                                "message": {
                                                    "type": "string"
                                                }
                                            }
                                        }
                                    ]
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}

Code sample

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Logs

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Dart version and used packages versions

3.4.3