gnucash maint: [assistant-stock-transaction] std::optional must be nullified

[Christopher Lam]

Updated	 via  https://github.com/Gnucash/gnucash/commit/3cb9fc5d (commit)
	from  https://github.com/Gnucash/gnucash/commit/7366de94 (commit)



commit 3cb9fc5d176bd923ed1203b6167b380c79eec904
Author: Christopher Lam <christopher.lck at gmail.com>
Date:   Sun Sep 4 16:24:41 2022 +0800

    [assistant-stock-transaction] std::optional must be nullified
    
    to release memory



Summary of changes:
 gnucash/gnome/assistant-stock-transaction.cpp | 3 +++
 1 file changed, 3 insertions(+)