[BUG] [KOTLIN] moshiCodeGen unable to handle additionalProperties: true

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

When using moshiCodeGen, and additionalProperties is set to true in the spec: additionalProperties: true, we are unable to successfully generate models.

Error preparing GetMessages200Response: com.squareup.moshi.kotlin.codegen.ksp.AppliedType.superclasses(AppliedType.kt:46)

openapi-generator version

Using 7.10.0. I don't believe its a regression.

OpenAPI declaration file content or url

      responses:
        "200":
          description: "Successful response"
          content:
            application/json:
              schema:
                type: object
                additionalProperties: true
                properties:
                  messages:
                    description: "Description"
                    nullable: false
                    type: array
                    items:
                      $ref: "#/components/schemas/Message"

Generation Details

Using the Kotlin generator with the gradle Plugin in an Android environment.

Steps to reproduce

1. Add additionalProperties: true to a model in your spec
2. Set moshiCodeGen to true

        additionalProperties.set(
            mapOf(
                Pair("moshiCodeGen", "true")
            )
        )

Related issues/PRs

Suggest a fix

Start with the Kotlin generator path and the Gradle plugin configuration that enables moshiCodeGen, reproducing the supplied schema with additionalProperties: true. Trace the model-generation path to the reported Moshi codegen error, then add coverage for this schema and verify that generation completes successfully.