OpenAPI 3.1.0 support: bug in JSON Schema 2020-12 hasKeyword function

[char0n]

This is related to hasKeyword function. The body of the function needs to change from

typeof schema === "object" && Object.hasOwn(schema, keyword)

To

schema !== null && typeof schema === "object" && Object.hasOwn(schema, keyword)

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Explanation: typeof null returns "object" and Object.hasOwn will throw if null is passed as first argument.