Schema with default: null becomes default("null") in generated Zod code

[robogeek]

Description

I have an OpenAPI spec where many of the object properties have default: null, such as these:

        programLongName:
          type: string
          description: Long name of program for human readability.
          example: Residential Time of Use-A
          nullable: true
          default: null
        retailerName:
          type: string
          description: Short name of energy retailer providing the program.
          example: ACME
          nullable: true
          default: null

In the generated TypeScript type, they look like:

  /**
   * Long name of program for human readability.
   *
   * @example Residential Time of Use-A
   * @default null
   */
  programLongName?: string | null;
  /**
   * Short name of energy retailer providing the program.
   *
   * @example ACME
   * @default null
   */
  retailerName?: string | null;

Then in the Zod code generated by ts-to-zod they look like:

  programLongName: z.string().optional().nullable().default("null"),
  retailerName: z.string().optional().nullable().default("null"),

The default should be null not "null".

Name	Version
openapi-codegen	8.0.0
ts-to-zod	3.4.1
Node.js	20.10.0
OS + version	Ubuntu 20.04

Reproduction

See above

Expected result

  programLongName: z.string().optional().nullable().default(null),
  retailerName: z.string().optional().nullable().default(null),