Can't update ComfyUI portable

### Expected Behavior

I use ComfyUI portable. It should update through the manager or through the update folder.

### Actual Behavior

ComfyUI never updates through the manager, therefore I've become used to the update folder. It now throws an error when trying to update.

### Steps to Reproduce

Download latest ComfyUI Windows standalone, try to update either through update folder or manager.

### Debug Logs

```powershell
Traceback (most recent call last):
File "E:\AI Apps\ComfyUI_Versions\ComfyUI_windows_portable_nvidia\ComfyUI_windows_portable\update\update.py", line 66, in
ref = repo.lookup_reference('refs/remotes/origin/master')
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
KeyError: 'refs/remotes/origin/master'
```

### Other

The line the error references:

ref = repo.lookup_reference('refs/remotes/origin/master')