fix(pe): show split alert only on splitting (backport #38440)

[mergify]

This is an automatic backport of pull request #38440 done by Mergify.
Cherry-pick of 96b13c5 has failed:

On branch mergify/bp/version-15-hotfix/pr-38440
Your branch is up to date with 'origin/version-15-hotfix'.

You are currently cherry-picking commit 96b13c59c1.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   erpnext/accounts/doctype/payment_entry/payment_entry.py

no changes added to commit (use "git add" and/or "git commit -a")

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

---

Mergify commands and options

More conditions and actions can be found in the documentation.

You can also trigger Mergify actions by commenting on this pull request:

• @Mergifyio refresh will re-evaluate the rules
• @Mergifyio rebase will rebase this PR on its base branch
• @Mergifyio update will merge the base branch into this PR
• @Mergifyio backport <destination> will backport this PR on <destination> branch

Additionally, on Mergify dashboard you can:

• look at your merge queues
• generate the Mergify configuration with the config editor.

Finally, you can contact us on https://mergify.com

[ruthra-kumar]

#37859 is not yet backported to v15

[marination]

@ruthra-kumar #38488 ported

[barredterra]

@Mergifyio update

[mergify]

update

☑️ Nothing to do

• -conflict [:pushpin: update requirement]
• #commits-behind>0 [:pushpin: update requirement]
• -closed [:pushpin: update requirement]