[BUG] [KOTLIN] Type with additionalProperties generates invalid code

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator?
• 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

In 7.16.0, using the Kotlin client generator with the multiplatform library, openapi-generator generates invalid code for types that have additionalProperties: {}. It adds an additional set of parentheses to the HashMap constructor invocation which makes the code not compile:

data class Abc (
...
) : kotlin.collections.HashMap<String, kotlin.Any>()() {
...

openapi-generator version

7.16.0, this worked in 7.15.0. I tried with latest master, still happens.

OpenAPI declaration file content or url

gist. I removed url etc, but otherwise this is 1:1 the real file we have.

Generation Details

java -jar openapi-generator-cli.jar generate -g kotlin -i openapi-issue.json --library multiplatform -o generated --additional-properties dateLibrary=string

Steps to reproduce

1. generate code (Kotlin, client, multiplatform)
2. open generated/src/commonMain/kotlin/org/openapitools/client/models/ProblemDetails.kt
3. notice the invalid kotlin.collections.HashMap<String, kotlin.Any>()()

Run the provided openapi-generator command with the linked OpenAPI declaration and inspect generated/src/commonMain/kotlin/org/openapitools/client/models/ProblemDetails.kt. Trace the Kotlin multiplatform generator path for additionalProperties, then verify that the generated HashMap inheritance is valid Kotlin and that the generated client compiles.