DOC: Add into about empty results in sample
As referred to in https://github.com/pandas-dev/pandas/issues/28495.

- [x] closes #28495
- [x] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Hello @roelhogervorst! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:



There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2019-09-24 06:44:10 UTC Can you provide something more descriptive? This as is is rather ambiguous Closing as stale but @roelhogervorst ping if you'd like to pick back up