[BUG] Asciidoc generate wrong null table cell value

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

Asciidoc generator generate wrong cell value in adoc, when the cell is empty!

openapi-generator version

7.17.0

OpenAPI declaration file content or url

      parameters:
        - name: applicantId
          in: path
          description: The unique identifier of the applicant
          required: true
          schema:
            type: string
            format: uuid

Generation Details

Generate wrong asciidoc table:

'''adoc
===== Parameters

====== Path Parameters

[cols="2,3,1,1,1"]
|===
|Name| Description| Required| Default| Pattern

| applicantId
| The unique identifier of the applicant
| X
| null
| |===

'''

Correct asciidoc table:

'''adoc
===== Parameters

====== Path Parameters

[cols="2,3,1,1,1"]
|===
|Name| Description| Required| Default| Pattern

| applicantId
| The unique identifier of the applicant
| X
| null
|
|===

'''

Steps to reproduce

Related issues/PRs

Suggest a fix

Start with the Asciidoc generator and reproduce the issue using the provided OpenAPI declaration for the applicantId path parameter. Compare the generated table with the expected output, focusing on the empty Pattern cell; done means the generated Asciidoc leaves that cell empty instead of emitting the wrong null value.