The `type` field must be defined when the `nullable` field is used.

Describe the bug
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I have an object "Discount" that has an attribute "type" that is an enum of Strings.

Discount: required: - type - percentages type: object properties: type: allOf: - $ref: '#/components/schemas/DiscountType' - description: Discount type enum: - INVOICE_EXPENSE - CONTRIBUTION_MARGIN - INVESTMENT example: INVESTMENT nullable: false percentages: description: Percentages and invoice amounts according to the type of discount minItems: 1 type: array items: $ref: '#/components/schemas/Percentage'

When I try to push my yaml file with the configuration above I get the error "The type field must be defined when the nullable field is used."

When I manually put "type: string" I am able to push it, but when I click to "Try it out" it gets an error in my "type" attribute.

On Swagger Editor I don't need to insert the "type: string" manually on my yaml file and when I click "Try it out" it works flawlessly.

Expected behavior
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Minimal reproducible OpenAPI snippet(if possible)

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Additional context
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Start with the provided Discount OpenAPI YAML, especially the type property using allOf, $ref, enum, and nullable. Reproduce the validation error and compare the behavior with Swagger Editor; done means the schema is accepted without an unnecessary type declaration and Try it out handles the field correctly.