Fix AutoVideoProcessor class lookup when torchvision is unavailable

[Abhijeetsingh610]

What does this PR do?

Fixes a crash in AutoVideoProcessor when torchvision is unavailable.

VIDEO_PROCESSOR_MAPPING_NAMES can contain None, and video_processor_class_from_name was doing if class_name in extractors, which raises TypeError for None.

This PR:

• skips None entries in video_processor_class_from_name
• adds a regression test in tests/models/auto/test_video_processing_auto.py

Fixes #43986 #43986

[github-actions]

[For maintainers] Suggested jobs to run (before merge)

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[christopher5106]

Hi,

Does this PR also solve this issue: huggingface/diffusers#13140 (comment)

?

Thanks

[Abhijeetsingh610]

Thanks for checking. Yes, this PR addresses the same root cause as huggingface/diffusers#13140.
In that issue, the crash happens in transformers.models.auto.video_processing_auto.video_processor_class_from_name when a mapping entry is None (typically when torchvision is unavailable) and code checks class_name in extractors.
This PR adds a None guard for that lookup and includes a regression test.
So once this is merged and released in transformers, that diffusers issue should be resolved when using the updated transformers version.

[Frojdholm]

@christopher5106 note that the root cause for the crash is you not having torchvision installed.

If your model requires a video processor it will not work since this will not create one. If the video processor is optional this might solve your issue.

[christopher5106]

@Frojdholm the bug appears on an image model, Qwen-Image and Qwen-Image-Edit. In that case, there is no video in inputs and outputs.