[BUG] [JAVA] [Gradle] '"additionalProperties": false' leads to failing code generation

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 have recently updated the openapi-generator gradle plugin from 6.6.0 to 7.1.0. Since then I have two problems, seemingly related to the use of "additionalProperties" in my swagger.json file.

• Case 1: If I have a definition with "additionalProperties": false, no java class will be generated for this defnition.
• Case 2: If I have a definition with "additionalProperties": false and a property that references the same definition, it will cause a StackOverflowError.

openapi-generator version

openapi-generator gradle plugin 7.1.0
It worked fine with version 6.6.0

OpenAPI declaration file content or url

• Case 1: https://raw.githubusercontent.com/sandra-thieme/openapi-generate-example/main/src/main/resources/swagger-no-generation.json
• Case2: https://github.com/sandra-thieme/openapi-generate-example/blob/main/src/main/resources/swagger-stackoverflow.json

Generation Details

I have created a minimal sample project to illustrate the issue: https://github.com/sandra-thieme/openapi-generate-example/tree/main. There are three swagger.json files in there: one that works, one that shows that nothing is generated (case 1), one that shows the stackoverflow error (case 2).

Steps to reproduce

In the above sample project:

• Call ./gradlew clean openApiGenerate
• Build succeeds but no class will have been generated in build/generated
• Change swagger-no-generation.json in build.gradle.kts to swagger-stackoverflow.json
• Call ./gradlew clean openApiGenerate
• Build fails with StackOverflowError

Related issues/PRs

Suggest a fix

Start with the linked sample project, its build.gradle.kts, and the swagger-no-generation.json and swagger-stackoverflow.json inputs. Run ./gradlew clean openApiGenerate for each case and compare the generated output and failure. Done means the first input generates its Java class and the self-referencing input completes without StackOverflowError.