BUG: not broadcasting when setting empty object
- [ ] closes #51450 (Replace xxxx with the GitHub issue number)
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- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

This is a regression on 1.5.x that we could get rid of because of changes since then. Should go into 2.0 instead of 1.5.x
> This is a regression on 1.5.x that we could get rid of because of changes since then. Should go into 2.0 instead of 1.5.x

can you expand a bit on this I tried removing the condition as I did here on 1.5.x and this does not work. Not overly interested in making an even more complex condition to accommodate all possible special cases on 1.5.x ok. The issue hasn't been triaged. Maybe worth commenting there. Thanks @phofl 