GPU acceleration gives gibberish output and breaks string grammars

# Prerequisites

Please answer the following questions for yourself before submitting an issue.

- [x] I am running the latest code. Development is very rapid so there are no tagged versions as of now.
- [x] I carefully followed the [README.md](https://github.com/abetlen/llama-cpp-python/blob/main/README.md).
- [x] I [searched using keywords relevant to my issue](https://docs.github.com/en/issues/tracking-your-work-with-issues/filtering-and-searching-issues-and-pull-requests) to make sure that I am creating a new issue that is not already open (or closed).
- [x] I reviewed the [Discussions](https://github.com/abetlen/llama-cpp-python/discussions), and have a new bug or useful enhancement to share.

# Expected Behavior

Model generates normal output when using GPU acceleration.

# Current Behavior

Model instead generates gibberish. Moreover, when using a grammar, the model encounters an assertion error.

For example, invoking the following code fragment:
```
from llama_cpp import Llama

llm = Llama(
model_path="./models/qwen2-7b-instruct-q5_k_m.gguf",
# n_gpu_layers=-1, # Uncomment to use GPU acceleration
seed=696969, # Uncomment to set a specific seed
n_ctx=32768, # Uncomment to increase the context window
)
output = llm(
"Q: Name the planets in the solar system? A: ", # Prompt
max_tokens=32, # Generate up to 32 tokens, set to None to generate up to the end of the context window
stop=["Q:", "\n"], # Stop generating just before the model would generate a new question
echo=True # Echo the prompt back in the output
) # Generate a completion, can also call create_completion
print(output)
```

With no GPU acceleration, the model produces the following output:
```
{'id': 'cmpl-8623a047-73a8-458b-9763-1a9f78f0fe04', 'object': 'text_completion', 'created': 1720787931, 'model': './models/qwen2-7b-instruct-q5_k_m.gguf', 'choices': [{'text': 'Q: Name the planets in the solar system? A: 1. Mercury 2. Venus 3. Earth 4. Mars 5. Jupiter 6. Saturn 7. Uranus 8. Neptune', 'index': 0, 'logprobs': None, 'finish_reason': 'length'}], 'usage': {'prompt_tokens': 13, 'completion_tokens': 32, 'total_tokens': 45}}
```

With GPU acceleration, the model produces the following output:
```
{'id': 'cmpl-b490a16d-d53b-4189-a5e6-40c4000425e9', 'object': 'text_completion', 'created': 1720787951, 'model': './models/qwen2-7b-instruct-q5_k_m.gguf', 'choices': [{'text': 'Q: Name the planets in the solar system? A: 1.GanG', 'index': 0, 'logprobs': None, 'finish_reason': 'stop'}], 'usage': {'prompt_tokens': 13, 'completion_tokens': 6, 'total_tokens': 19}}
```

Additionally, when using a string grammar, I encountered this assertion error:
```
GGML_ASSERT: C:\Users\minhk\AppData\Local\Temp\pip-install-h1m08tsi\llama-cpp-python_e9c0081b84634f459b14411750bdc6a0\vendor\llama.cpp\src\llama.cpp:17594: !grammar->stacks.empty()
```

# Environment and Context

My laptop has a NVIDIA GeForce GTX 4060 GPU and is running with CUDA 12.5.1.
OS: Windows 11 Home version 10.0.22621 build 22621.

Python version:
```
python --version
```
```
Python 3.12.1
```

Make version:
```
make --version
```
```
GNU Make 4.4.1
Built for Windows32
Copyright (C) 1988-2023 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
```

GCC version:
```
g++ --version
```
```
g++.exe (MinGW-W64 x86_64-ucrt-posix-seh, built by Brecht Sanders) 12.3.0
Copyright (C) 2022 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
```

# Failure Information (for bugs)

Please help provide information about the failure if this is a bug. If it is not a bug, please remove the rest of this template.

# Steps to Reproduce

1. Install `llama-cpp-python` with CUDA.
2. Use [Qwen2-7B-Instruct](https://huggingface.co/Qwen/Qwen2-7B-Instruct) model

# Failure Logs

There are no failure logs - the program just returns nonsensical output.

The issue is in GPU acceleration causing gibberish output and breaking grammars. Start by examining the CUDA build of llama-cpp-python, specifically the GPU layer offloading. Look at the vendor/llama.cpp/src/llama.cpp file around line 17594 for the grammar stack assertion. Reproduce with the provided Qwen2 model and compare CPU vs GPU inference paths. Check for any known issues with Windows CUDA 12.5 and the specific GPU architecture.

Written by the indexing model from the issue text.