refactor: Fix clang compile failure
Summary:
script/standard.cpp:278:22: error: default initialization of an object of const type 'const (anonymous namespace)::CScriptVisitor' without a user-provided default constructor
const CScriptVisitor g_script_visitor;
^
{}
1 error generated.This is a backport of core#19333 and core#19428
Test Plan: ninja all check-all
Reviewers: #bitcoin_abc, majcosta, Fabien
Reviewed By: #bitcoin_abc, majcosta, Fabien
Subscribers: Fabien, majcosta
Differential Revision: https://reviews.bitcoinabc.org/D9966