Add key to indicate checkpoint is v_prediction when saving.

comfy/model_base.py

@@ -99,6 +99,10 @@ class BaseModel(torch.nn.Module):
         if self.get_dtype() == torch.float16:
             clip_state_dict = utils.convert_sd_to(clip_state_dict, torch.float16)
             vae_state_dict = utils.convert_sd_to(vae_state_dict, torch.float16)
+
+        if self.model_type == ModelType.V_PREDICTION:
+            unet_state_dict["v_pred"] = torch.tensor([])
+
         return {**unet_state_dict, **vae_state_dict, **clip_state_dict}