panic: `no entry found for key` with invalid type expression

### Summary

ty crashes when checking this fuzzed code:

```python
_: "a*(_ for _ in _)"
```

```
error[panic]: Panicked at crates/ty_python_semantic/src/types/infer/builder.rs:7815:14 when checking `/home/user/a.py`: `no entry found for key`
```

### Version

35e23aa w/ astral-sh/ruff@1b44d7e