Error: Could not detect model type when loading checkpoint

### Expected Behavior

The checkpoint "flux1-dev-fp8.safetensors" should load successfully using the CheckpointLoaderSimple node.

### Actual Behavior

An error occurs when attempting to load the checkpoint, stating "ERROR: Could not detect model type of: [path]/models/checkpoints/flux1-dev-fp8.safetensors"

### Steps to Reproduce

1. Attempt to load the checkpoint "flux1-dev-fp8.safetensors" using CheckpointLoaderSimple node
2. Queue the workflow

### Debug Logs

```powershell
Error occurred when executing CheckpointLoaderSimple: ERROR: Could not detect model type of: [path]/models/checkpoints/flux1-dev-fp8.safetensors
File "[path]/execution.py", line 152, in recursive_execute
output_data, output_ui = get_output_data(obj, input_data_all)
File "[path]/execution.py", line 82, in get_output_data
return_values = map_node_over_list(obj, input_data_all, obj.FUNCTION, allow_interrupt=True)
File "[path]/execution.py", line 75, in map_node_over_list
results.append(getattr(obj, func)(**slice_dict(input_data_all, i)))
File "[path]/nodes.py", line 518, in load_checkpoint
out = comfy.sd.load_checkpoint_guess_config(ckpt_path, output_vae=True, output_clip=True, embedding_directory=folder_paths.get_folder_paths("embeddings"))
File "[path]/comfy/sd.py", line 513, in load_checkpoint_guess_config
raise RuntimeError("ERROR: Could not detect model type of: {}".format(ckpt_path))
```
I'm on the newest version of ComfyUI, I know this because I cloned master a few mins back and copied the models and custom_nodes dirs and tried it again. Also ComfyUI Manager says I'm up to date.