Handle the None case for the model_dtype (Fixes GGUF + Lora crash)

[rattus128]

There are paths where this can be None. Default to fp32 in that case.

https://discordapp.com/channels/1218270712402415686/1243610878314807337/1447705628758904832

[comfyanonymous]

Already fixed: 3b0368a

manual_cast_dtype set to None means there's no cast so it should default to the weight dtype right?

[rattus128]

Already fixed: 3b0368a

manual_cast_dtype set to None means there's no cast so it should default to the weight dtype right?

Yes that makes sense. I think the problem im actually chasing here is when X comes in at a higher dtype than the model and forces this cast which still needs implementation. This is self consistent with figuring out casts for the sake of the model types.

Closing.