BUG: cumulative functions with ea dtype not handling NA correctly and casting to object
- [x] closes #39479
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [x] whatsnew entry

More general solution is being worked on in https://github.com/pandas-dev/pandas/pull/28509 (which doesn't mean a short term solution can't be merged, I didn't closely look at either PR, just noting) 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. > More general solution is being worked on in #28509 (which doesn't mean a short term solution can't be merged, I didn't closely look at either PR, just noting)

@phofl can you resolve conflicts @phofl closing as stale. https://github.com/pandas-dev/pandas/pull/39483#discussion_r593823587 needs addressing. reopen when ready.