[BUG][typescript-angular] `queryParamObjectFormat` is non-compliant with `tsc --strictNullChecks`

Created by: snebjorn

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

Generating with the queryParamObjectFormat additional property causes the generated code to be non-compilable with the strictNullChecks typescript compile flag.

openapi-generator version

6.1.0

OpenAPI declaration file content or url

https://github.com/snebjorn/openapi-gen-bug/blob/master/compile-bug.json

{
  "openapi": "3.0.0",
  "info": {
    "title": "",
    "version": ""
  },
  "paths": {
    "/Foos": {
      "get": {
        "responses": {
          "200": {
            "description": ""
          }
        }
      }
    }
  }
}

Generation Details

Generate with queryParamObjectFormat: json https://github.com/snebjorn/openapi-gen-bug/blob/ee78e17b3e1e8369eed090b4ab4694d3b34ee84d/openapitools.json#L30-L36

Steps to reproduce

1. Clone https://github.com/snebjorn/openapi-gen-bug
2. Run yarn install
3. Run yarn gen
4. Run yarn err
5. Observe compile error

Related issues/PRs

https://github.com/OpenAPITools/openapi-generator/issues/10844 is somewhat related

Suggest a fix

Ideally generated code should comply with the --strict rule set of TypeScript.

However a quick fix for this issue is to do what is done on literally the next line in the code

if (typeof value === "object") {
    httpParams = httpParams.append(key, JSON.stringify(value));
} else if (key != null) { // <-------------------------------------------- NOTICE
    httpParams = httpParams.append(key, value);
}

Just check that key isn't null. append doesn't accept null or undefined anyway.