[BUG][SCALA-AKKA] Doesn't generate models when defined inline (reproduced for java & scala-akka)

Created by: Coder-DG

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? No models generated vs models generated
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Description

Running java -jar openapi-generator-cli.jar generate -i 'swagger.json' -g scala-akka -o scala_client --generate-alias-as-model (also without config and/or without --generate-alias-as-model), doesn't produce any model libs.

Removing "additionalProperties": false, from the inline schema def makes it generate model classes. What also works is to define the schema using definitions + "$ref" : "..." - but that's not really feasible with the library I'm using for my server.

openapi-generator version

5.0.1 and also tested with openapi-generator-cli-5.1.0-20210304.083949-99.jar

OpenAPI declaration file content or url

swagger.json gist

Generation Details

Steps to reproduce

Just run java -jar openapi-generator-cli.jar generate -i 'swagger.json' -g scala-akka -o scala_client where swagger.json is the file I linked above, and the jar is either 5.0.1 or the snapshot version I mentioned.

Related issues/PRs

Suggest a fix

Somehow removing "additionalProperties": false, from the inline schema def makes it generate model classes. Setting it to true doesn't help either (not sure true is valid though). Referencing it with "$ref": "..." and moving the schema to definitions also solves this (but I can't use that solution due to the. lib I'm using).