llm_chat_create() SEG FAULT  without llm_context_create()

This crashes with SEG FAULT:

```
SELECT llm_model_load('/home/sqlitecloud/repositories/sqlite-rag/models/unsloth/gemma-3-270m-it-GGUF/gemma-3-270m-it-Q8_0.gguf');
SELECT llm_chat_create();
```

This works:
```
SELECT llm_model_load('/home/sqlitecloud/repositories/sqlite-rag/models/unsloth/gemma-3-270m-it-GGUF/gemma-3-270m-it-Q8_0.gguf');
SELECT llm_context_create();
SELECT llm_chat_create();
```