gnucash stable: [gnc-budget] use std::optional<gnc_numeric> instead of bool+gnc_numeric

[Christopher Lam]

Updated	 via  https://github.com/Gnucash/gnucash/commit/1d26d99d (commit)
	from  https://github.com/Gnucash/gnucash/commit/2db3a6ba (commit)



commit 1d26d99ddb9baa2f59dd9fa347d8f65ab15e0ed6
Author: Christopher Lam <christopher.lck at gmail.com>
Date:   Fri Nov 17 21:08:14 2023 +0800

    [gnc-budget] use std::optional<gnc_numeric> instead of bool+gnc_numeric
    
    more expressive



Summary of changes:
 libgnucash/engine/gnc-budget.cpp | 26 +++++++++++---------------
 1 file changed, 11 insertions(+), 15 deletions(-)