[typescript] Incorrect extends null<...> declaration for map/dictionary-like schema definitions with additionalProperties

[softworkz]

OpenApi Schema

    "MyDictionary": {
      "type": "object",
      "additionalProperties": {
        "type": "string"
      }
    }

Generated TypeScript

/**
 * 
 * @export
 * @interface ProviderIdDictionary
 */
export interface ProviderIdDictionary extends null<String, string> {
    [key: string]: string;
}

[softworkz]

Related: #691

@micryc @frantuma - The related issue is 4 years old. Is there any chance to get this fixed?