BUG: Fixes plotting with nullable integers (#32073)
- [x] closes #32073
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry



This is the first time I am contributing to pandas open source project. Please let me know if I can improve anything on this commit.  @jreback the branch has the latest code and all the checks passed.  thanks @rkc007 