Fix: Safe handling for multimodal_config to avoid 'NoneType' object h…

[qibaoyuan]

PLEASE FILL IN THE PR DESCRIPTION HERE ENSURING ALL CHECKLIST ITEMS (AT THE BOTTOM) HAVE BEEN CONSIDERED.

Purpose

This PR fixes an issue where multimodal_config may be None, causing:

AttributeError: 'NoneType' object has no attribute '__dict__'

The original implementation assumes that multimodal_config is always an object with a dict attribute, but in real configurations it may be:

None

A dict

An object with attributes

This PR adds a safe, concise one-line implementation that supports all cases without changing existing behavior.

Test Plan

Initialize Omni model with:

multimodal_config = None

multimodal_config = {}

multimodal_config = {"foo": "bar"}

custom multimodal config objects

Test Result

All cases load successfully.

---

Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.
• (Optional) Release notes update. If your change is user facing, please update the release notes draft.

BEFORE SUBMITTING, PLEASE READ https://github.com/vllm-project/vllm-omni/blob/main/CONTRIBUTING.md (anything written below this line will be removed by GitHub Actions)

[hsliuustc0106]

lgtm, thx