[BUG][Dart] ApiException 500: Exception during deserialization.

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

Issue:
When generating num.parse in native_class.mustache for a nullable num type, the following error occurs during deserialization:
Error while fetching
ApiException 500: Exception during deserialization. (Inner exception: FormatException: null)

A type is also nullable when "required" and "defaultValue" is false:

The problem is that this is not taken into account for num.parse:

Suggestion:
Change Lines:

        {{{name}}}: {{#isNullable}}json[r'{{{baseName}}}'] == null
            ? {{#defaultValue}}{{{.}}}{{/defaultValue}}{{^defaultValue}}null{{/defaultValue}}
            : {{/isNullable}}{{{datatypeWithEnum}}}.parse('${json[r'{{{baseName}}}']}'),

With Lines:

        {{{name}}}: {{#isNullable}}json[r'{{{baseName}}}'] == null
            ? {{#defaultValue}}{{{.}}}{{/defaultValue}}{{^defaultValue}}null{{/defaultValue}}
            : {{/isNullable}}{{^isNullable}}{{^required}}{{^defaultValue}}json[r'{{{baseName}}}'] == null
            ? {{#defaultValue}}{{{.}}}{{/defaultValue}}{{^defaultValue}}null{{/defaultValue}}
            : {{/defaultValue}}{{/required}}{{/isNullable}}{{{datatypeWithEnum}}}.parse('${json[r'{{{baseName}}}']}'),

openapi-generator version

7.10.0

OpenAPI declaration file content or url

{
  "openapi": "3.0.1",
  "components": {
    "schemas": {
      "Test": {
        "required": [
          "number",
          "subNumber"
        ],
        "type": "object",
        "properties": {
          "id": {
            "type": "string",
            "readOnly": true
          },
          "problem": {
            "type": "number"
          }
        }
      }
    }
  }
}

Steps to reproduce

Try to deserialize the object Test with OpenAPI and get Error for "problem" with type "number".

Start with the num deserialization in native_class.mustache and reproduce the issue using the provided OpenAPI declaration, focusing on the nullable problem number field. Compare the generated Dart handling with the reported suggestion; done means deserializing an omitted nullable number no longer raises a FormatException.