## Summary

Follow-up to #15394. See [this review
comment](#15394 (comment)).

## Test Plan

`cargo nextest run` and `cargo insta test`.

…tionary is empty (`PIE800`) (#16008)

## Summary

Resolves #15997.

Ruff used to introduce syntax errors while fixing these cases, but no
longer will:

```python
{"a": [], **{},}
#         ^^^^ Removed, leaving two contiguous commas

{"a": [], **({})}
#         ^^^^^ Removed, leaving a stray closing parentheses
```

Previously, the function would take a shortcut if the unpacked
dictionary is empty; now, both cases are handled using the same logic
introduced in #15394. This change slightly modifies that logic to also
remove the first comma following the dictionary, if and only if it is
empty.

## Test Plan

`cargo nextest run` and `cargo insta test`.