BUG: merge between partial index and index fails when result is empty
- [x] closes #33814
- [x] tests added / passed
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

The Issue was caused when setting the name of an numpy array.
This pull request is stale because it has been open for thirty days with no activity. Please update or respond to this comment if you're still interested in working on this. Done @jreback green thanks @phofl 