Flux loading issue, when the workflow is changed 

### Expected Behavior

Don't load Flux again, when the workflow is changed

### Actual Behavior

The model is loaded again, unnecessarily

### Steps to Reproduce

- Use Flux with the checkpoint loader. 
- Switch to an older Flux checkpoint with the Unet loader.   
- Before running the queue, replace the Unet loader, with checkpoint loader, to keep using the same model. 

But the Flux model will load again, and since RAM is already full from the previous workflow, the page file needs to increase massively, reducing available SSD space, for a while.  

### Debug Logs

```powershell
.
```

### Other

_No response_