Tokenizer force unwraps an optional that's nil for Gemma

[ViRo3]

st.txt

Steps :

1. https://github.com/ml-explore/mlx-swift-examples/tree/main/Applications/LLMEval Change LLMEvaluator to use gemma
2. Prompt : "Write code to boot raspberry pico pi"
3. Bug

Related : ml-explore/mlx-swift-examples#50

[pcuenca]

Thanks for the report and the extra context, I'll take a look soon!