fix: Presentation currency conversion in reports (backport #27316)

[mergify]

As shown in the image above there could be cases where a single GL might have both Debit and Credit values

Currently, the function used to convert values to presentation currency assumed that one GL Entry will either have debit or credit value while led to wrong values in the reports when a presentation currency was selected

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This is an automatic backport of pull request #27316 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of ceaa804 has failed:

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	both modified:   erpnext/accounts/report/utils.py

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