[BUG] Erroneous error expecting `items` field on component schema

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

I am trying to generate client code for a schema, but it gives me an error saying

attribute components.schemas.Config.items is missing

This is confusing to me, as the 3.0.3 spec says:

items - Value MUST be an object and not an array. Inline or referenced schema MUST be of a Schema Object and not a standard JSON Schema. items MUST be present if the type is array.
The type is not array, so I do not understand why it claims it is missing.

openapi-generator version

openapi-generator-cli 5.3.0
  commit : bb124e1
  built  : 2021-10-24T14:50:41Z
  source : https://github.com/openapitools/openapi-generator
  docs   : https://openapi-generator.tech/

OpenAPI declaration file content or url

openapi: '3.0.3'
info:
  version: 1.0.0
  title: Minimal Repro
paths:
  /ping:
    get:
      responses:
        '200':
          description: OK
components:
  schemas:
    Config:
      title: Config
      type: object
      properties:
        myProperty:
          type: array
          default: [a, b, c]

Steps to reproduce

• Try to validate the above spec

Start with the minimal OpenAPI 3.0.3 YAML in the issue and reproduce the validation error using openapi-generator-cli 5.3.0. Trace the schema validation path for components.schemas.Config and its array property; done means the valid non-array schema no longer reports a missing items field and the reproduction is covered by a regression check.