"model_type" error when encountering "items": false

Start by reproducing the model_type error with the OpenAPI 3.1 specification included in the issue, focusing on the nested array schema where items is false and prefixItems is present. Trace the schema parsing or validation path that assumes items is a dictionary. Done means the supplied specification parses successfully and a regression test covers this tuple form.

Describe the bug
According to the openapi 3.1 specification, tuples should be modeled using the "prefixItems" field with the "items" field being set to false (spec).

However this causes a "model_type" error as the generator expects the "items" field to be a dictionary.

OpenAPI Spec File

{
    "openapi": "3.1.0",
    "info": {
        "title": "foobar",
        "description": "",
        "license": {
            "name": ""
        },
        "version": "0.1.0"
    },
    "paths": {
        "/my/path": {
            "get": {
                "description": "foo",
                "operationId": "bar",
                "parameters": [],
                "responses": {
                    "200": {
                        "description": "",
                        "content": {
                            "application/json": {
                                "schema": {
                                    "type": "array",
                                    "items": {
                                        "type": "array",
                                        "items": false,
                                        "prefixItems": [
                                            {
                                                "type": "string",
                                                "format": "date-time"
                                            },
                                            {}
                                        ]
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}

Removing the "items": false causes the file to parse successfully.

Desktop (please complete the following information):

• OS: Ubuntu 22.04.5 LTS
• Python Version: 3.10.12
• openapi-python-client version 0.24.1