fix: ensure casting to torch.uint8

[dnswd]

Fixes #3539

[comfyanonymous]

if you do:

        latents_ubyte = latents_ubyte.to(device="cpu", dtype=torch.uint8, non_blocking=comfy.model_management.device_supports_non_blocking(latent_image.device))
        latents_ubyte = latents_ubyte.to(dtype=torch.uint8)

does it also work?

[dnswd]

I tried it again and the previews are just dots of rgb, but it doesn't seem to have any error

[dnswd]

Closed in favor of #3583