fix: set empty value for tax template in item details (backport #37496)

[mergify]

This is an automatic backport of pull request #37496 done by Mergify.
Cherry-pick of b0d440c has failed:

On branch mergify/bp/version-14-hotfix/pr-37496
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Changes to be committed:
	modified:   erpnext/accounts/doctype/sales_invoice/test_sales_invoice.py
	modified:   erpnext/stock/doctype/item/test_item.py
	modified:   erpnext/stock/get_item_details.py

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

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

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[frappe-pr-bot]

🎉 This PR is included in version 14.46.0 🎉

The release is available on GitHub release

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