Disable gradients on diffusion models. (#15218)

comfy/model_base.py

@@ -169,6 +169,7 @@ class BaseModel(torch.nn.Module):
             else:
                 operations = model_config.custom_operations
             self.diffusion_model = unet_model(**unet_config, device=device, operations=operations)
+            self.diffusion_model.requires_grad_(False)
             self.diffusion_model.eval()
             if comfy.model_management.force_channels_last():
                 self.diffusion_model.to(memory_format=torch.channels_last)