[Type Check] for Qwen-Image-Edit and Wan

[Jayce-Ping]

What does this PR do?

Issues:

In Qwen-Image-Edit-Plus pipeline, if there is no image input, the variables condition_image_sizes, condition_images, vae_image_sizes and vae_images are not assigned but used. And the check_input method does not really make sure image is not None either.

In Wan series related pipeline, the actually used scheduler is UniPCMultistepScheduler rather thanFlowMatchEulerDiscreteScheduler, which is correct in docstring but with wrong type hint. It is confusing for readers.

Fixes:
Assign relevant variables with initial value None and it also makes it possible for Qwen-Image-Edit-Plus pipeline to be text-to-image compatible in the future.

For Wan, just fix the type hints.

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