gguf_file breaks for AutoTokenizer.from_pretrained and AutoModelForCausalLM.from_pretrained
Author: xenova
Pull request: no
Labels: name: bug

### System Info

- `transformers` version: 5.0.0.dev0
- Platform: macOS-15.6-arm64-arm-64bit-Mach-O
- Python version: 3.13.2
- Huggingface_hub version: 1.3.1
- Safetensors version: 0.5.3
- Accelerate version: 1.12.0
- Accelerate config:    not found
- DeepSpeed version: not installed
- PyTorch version (accelerator?): 2.9.0 (NA)
- Using distributed or parallel set-up in script?: no


### Who can help?

@ArthurZucker @itazap (from https://github.com/huggingface/transformers/pull/40936)
@LysandreJik (from https://github.com/huggingface/transformers/pull/30391)


### Information

- [ ] The official example scripts
- [ ] My own modified scripts

### Tasks

- [ ] An officially supported task in the `examples` folder (such as GLUE/SQuAD, ...)
- [ ] My own task or dataset (give details below)

### Reproduction

Following https://huggingface.co/docs/transformers/en/gguf, run
```py
import torch
from transformers import AutoTokenizer, AutoModelForCausalLM

model_id = "sweepai/sweep-next-edit-1.5B"
filename = "sweep-next-edit-1.5b.q8_0.v2.gguf"

dtype = torch.float32 # could be torch.float16 or torch.bfloat16 too
tokenizer = AutoTokenizer.from_pretrained(model_id, gguf_file=filename)
model = AutoModelForCausalLM.from_pretrained(model_id, gguf_file=filename, dtype=dtype)
```

Encounter error #1:
```
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    tokenizer = AutoTokenizer.from_pretrained(model_id, gguf_file=filename)
  File ".../transformers/models/auto/tokenization_auto.py", line 726, in from_pretrained
    return tokenizer_class.from_pretrained(pretrained_model_name_or_path, *inputs, **kwargs)
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".../transformers/tokenization_utils_base.py", line 1646, in from_pretrained
    vocab_files = {**cls.vocab_files_names, **additional_files_names}
                                              ^^^^^^^^^^^^^^^^^^^^^^
UnboundLocalError: cannot access local variable 'additional_files_names' where it is not associated with a value
```

After replacing if gguf_file section with
```py
                additional_files_names = {
                    "vocab_file": gguf_file,
                }
```
We still get another error:
```
  File ".../transformers/tokenization_utils_base.py", line 2004, in _from_pretrained
    tokenizer = cls(*init_inputs, **init_kwargs)
  File ".../transformers/models/qwen2/tokenization_qwen2.py", line 65, in __init__
    BPE(
    ~~~^
        vocab=self._vocab,
        ^^^^^^^^^^^^^^^^^^
    ...<6 lines>...
        byte_fallback=False,
        ^^^^^^^^^^^^^^^^^^^^
    )
    ^
ValueError: `vocab` and `merges` must be both be from memory or both filenames
```


### Expected behavior

The conversion should run correctly and we should be able to load the model and tokenizer.

Comments:
FWIW,
```py
model = AutoModelForCausalLM.from_pretrained(model_id, gguf_file=filename, dtype=dtype)
```
also breaks with a different error, but it can be bypassed by specifying
```py
from transformers import AutoModelForCausalLM, GenerationConfig

...
model = AutoModelForCausalLM.from_pretrained(model_id, gguf_file=filename, dtype=dtype, generation_config=GenerationConfig())
```

Indeed, on it