Fix for #12723: Unexpected behavior with binary operators and fill…
- [ ] closes #xxxx
- [x] tests added / passed
- [x] passes `git diff upstream/master | flake8 --diff`
- [x] whatsnew entry

closes #12723 

If it is OK, I'd like to add a whatsnew and rebase.
 pls test for the sparse cases as well
 The work is done if all tests are passed. 
Thanks, everyone.
 If it is ok, 
might we close #12723 ?
 issues are closed when the PRs are merged - I'll have a look soon
 thanks for the fix!
