Error running openpose：'set' object has no attribute 'append'

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### Checklist

- [ ] The issue exists after disabling all extensions
- [ ] The issue exists on a clean installation of webui
- [ ] The issue is caused by an extension, but I believe it is caused by a bug in the webui
- [ ] The issue exists in the current version of the webui
- [x] The issue has not been reported before recently
- [ ] The issue has been reported before but has not been fixed yet

### What happened?

Error running openpose：'set' object has no attribute 'append'

### Steps to reproduce the problem

1.enable Controlnet openpose
2.Preview

### What should have happened?

Error appears on the page

### What browsers do you use to access the UI ?

Google Chrome

### Sysinfo

TypeError: 'NoneType' object is not iterable

### Console logs

```Shell
Traceback (most recent call last):
File "/root/miniconda3/lib/python3.10/site-packages/gradio/routes.py", line 488, in run_predict
output = await app.get_blocks().process_api(
File "/root/miniconda3/lib/python3.10/site-packages/gradio/blocks.py", line 1431, in process_api
result = await self.call_function(
File "/root/miniconda3/lib/python3.10/site-packages/gradio/blocks.py", line 1103, in call_function
prediction = await anyio.to_thread.run_sync(
File "/root/miniconda3/lib/python3.10/site-packages/anyio/to_thread.py", line 33, in run_sync
return await get_asynclib().run_sync_in_worker_thread(
File "/root/miniconda3/lib/python3.10/site-packages/anyio/_backends/_asyncio.py", line 877, in run_sync_in_worker_thread
return await future
File "/root/miniconda3/lib/python3.10/site-packages/anyio/_backends/_asyncio.py", line 807, in run
result = context.run(func, *args)
File "/root/miniconda3/lib/python3.10/site-packages/gradio/utils.py", line 707, in wrapper
response = f(*args, **kwargs)
File "/root/stable-diffusion-webui-forge-main/extensions-builtin/sd_forge_controlnet/lib_controlnet/controlnet_ui/controlnet_ui_group.py", line 847, in run_annotator
result = preprocessor(
File "/root/stable-diffusion-webui-forge-main/extensions-builtin/forge_legacy_preprocessors/scripts/legacy_preprocessors.py", line 103, in __call__
result, is_image = self.call_function(img=input_image, res=resolution, thr_a=slider_1, thr_b=slider_2, **kwargs)
File "/root/stable-diffusion-webui-forge-main/extensions-builtin/forge_legacy_preprocessors/legacy_preprocessors/preprocessor.py", line 291, in run_model
return remove_pad(self.model_openpose(
File "/root/stable-diffusion-webui-forge-main/extensions-builtin/forge_legacy_preprocessors/annotator/openpose/__init__.py", line 447, in __call__
poses = self.detect_poses(oriImg, include_hand, include_face)
File "/root/stable-diffusion-webui-forge-main/extensions-builtin/forge_legacy_preprocessors/annotator/openpose/__init__.py", line 335, in detect_poses
self.body_estimation.model.to(self.device)
File "/root/stable-diffusion-webui-forge-main/modules_forge/ops.py", line 26, in patched_to
return original_to(self, *args, **kwargs)
File "/root/stable-diffusion-webui-forge-main/modules_forge/ops.py", line 25, in patched_to
module_list.append(self)
AttributeError: 'set' object has no attribute 'append'
```

### Additional information

_No response_

Start in modules_forge/ops.py at patched_to, where the traceback reports module_list.append(self), then trace how module_list is initialized during the OpenPose preview path in extensions-builtin/forge_legacy_preprocessors/annotator/openpose/__init__.py. Reproduce the failure by enabling ControlNet OpenPose and selecting Preview; done means the preview completes without the reported AttributeError.

Written by the indexing model from the issue text.