extra_model_paths config not working

### Custom Node Testing

- [x] 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

While using a file `extra_model_paths.yaml` in the ComfyUI main directory with content
```
base_path: /home/user/otherAI/SD
checkpoints: Models/StableDiffusion
loras: Models/Lora
vae: Models/VAE
vae_approx: Models/ApproxVAE
text_encoders: Models/TextEncoders
```
I would expect, that ComfyUI is starting with acces to the models in the described paths.

### Actual Behavior

Instead while starting immediatly an error is thrown and the execution stops:
```
Traceback (most recent call last):
File "/home/sd/AI/Packages/ComfyUI/main.py", line 158, in
apply_custom_paths()
File "/home/sd/AI/Packages/ComfyUI/main.py", line 79, in apply_custom_paths
utils.extra_config.load_extra_path_config(extra_model_paths_config_path)
File "/home/sd/AI/Packages/ComfyUI/utils/extra_config.py", line 29, in load_extra_path_config
for y in conf[x].split("\n"):
~~~~^^^
TypeError: string indices must be integers, not 'str'
```

### Steps to Reproduce

Just move some models into a path, different from ComfyUI.
Try to use the described configuration.
Use the same configuration for `extra_model_paths.yaml`
Start main.py (with activated venv ...).
Look for errors.

### Debug Logs

```powershell
Traceback (most recent call last):
File "/home/sd/AI/Packages/ComfyUI/main.py", line 158, in
apply_custom_paths()
File "/home/sd/AI/Packages/ComfyUI/main.py", line 79, in apply_custom_paths
utils.extra_config.load_extra_path_config(extra_model_paths_config_path)
File "/home/sd/AI/Packages/ComfyUI/utils/extra_config.py", line 29, in load_extra_path_config
for y in conf[x].split("\n"):
~~~~^^^
TypeError: string indices must be integers, not 'str'
```

### Other

Operating System: Ubuntu Studio 24.04
KDE Plasma Version: 5.27.12
KDE Frameworks Version: 5.115.0
Qt Version: 5.15.13
Kernel Version: 6.14.0-37-generic (64-bit)
Graphics Platform: X11
Processors: 16 × 13th Gen Intel® Core™ i7-13700K
Memory: 62.5 GiB of RAM
Graphics Processor: NVIDIA GeForce RTX 4060 Ti/PCIe/SSE2
Manufacturer: ASUS