[Minor Fix] Fix llava modalities issue for single-image

[kcz358]

Motivation

As described in #1400 , LLaVA is performing worse under single-image evaluation

Modifications

Fix the condition issue when forwarding single-image using llava. Adapt the new modalities parameters with single-image

Checklist

• Format your code according to the Contributor Guide.
• Add unit tests as outlined in the Contributor Guide.
• Update documentation as needed, including docstrings or example tutorials.

[kcz358]

Alignment result

AI2D

MME