Fix read_sql empty result with chunksize bug GH34411
- [x ] closes #34411
- [ x] tests added / passed
- [ x] passes `black pandas`
- [ x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ x] whatsnew entry

`pd.read_sql` was returning an empty generator when chunksize is set and the query returns zero results. Now it correctly returns a generator with a single empty DataFrame (:issue:`34411`).