KeyError: 'facets'

Sometimes I get a key error on `facets`, I could not reproduce it. I am wondering if this is something normal and if you know in what condition it could happen ?

```python
results = index.search("", {"facets": "*"})
facets = results['facets'] # <== sometimes the key is not present
```

Start with the `index.search("", {"facets": "*"})` example and inspect how the Python client constructs and returns search results. Reproduce the missing `facets` key if possible, then identify and document the condition or behavior that explains it and add an appropriate regression check if the repository provides one.

Written by the indexing model from the issue text.