Why does a mask layer get inserted into the interface after startup?

### Custom Node Testing

- [ ] I have tried disabling custom nodes and the issue persists (see [how to disable custom nodes](https://docs.comfy.org/troubleshooting/custom-node-issues#step-1%3A-test-with-all-custom-nodes-disabled) if you need help)

### Expected Behavior

Why does a mask layer get inserted into the interface after startup?
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### Actual Behavior

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Why does a mask layer get inserted into the interface after startup?
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### Steps to Reproduce

Why does a mask layer get inserted into the interface after startup?

### Debug Logs

```powershell
Why does a mask layer get inserted into the interface after startup?
```

### Other

_No response_