fix: manually added weight per unit reset to zero after save (backport #27330)

[mergify]

Due to recent changes, manually set weight per unit reset to zero.

When user make the delivery from the sales order, they manually set the Weight Per Unit against the item but after saving of the delivery note the rate reset to zero.

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This is an automatic backport of pull request #27330 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 7b4a654 has failed:

On branch mergify/bp/version-13-hotfix/pr-27330
Your branch is up to date with 'origin/version-13-hotfix'.

You are currently cherry-picking commit 7b4a65484a.
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Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   erpnext/public/js/controllers/transaction.js
	both modified:   erpnext/stock/get_item_details.py

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

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