fix edge case with PIE804 (#7922)
## Summary
`foo(**{})` was an overlooked edge case for `PIE804` which introduced a
crash within the Fix, introduced in #7884.
I've made it so that `foo(**{})` turns into `foo()` when applied with
`--fix`, but is that desired/expected? 🤔 Should we just ignore instead?
## Test Plan
`cargo test`
