panic: `index out of bounds: the len is 8 but the index is 16479`

### Summary

ty crashes when checking this fuzzed code:

```python
__next__ = next
@staticmethod
def __next__
```

```
error[panic]: Panicked at crates/ruff_db/src/parsed.rs:210:13 when checking `/home/user/a.py`: `index out of bounds: the len is 8 but the index is 16479`
```

### Version

5e31bc9 w/ astral-sh/ruff@bc8efa2fd86