Fix BUG: DataFrame.shift with freq on empty DataFrames
- [ ] closes #60102

This PR addresses the issue where `DataFrame.shift` with `freq` on an empty DataFrame doesn't shift the index. 

**Discussion:**
I’m a beginner, and I’m not entirely sure if my changes meet the community’s standards. If there are any areas where my modifications could be improved or aren’t quite right, I would be very grateful for any feedback you can provide. I’m eager to learn and make adjustments as needed. Thanks for your understanding!

I apologize for mistakenly selecting the option to request a merge. I know there are still issues with my code and it cannot be merged, but I accidentally clicked the option to request a merge.And I don't know what I can do now.