m_svgIcon can be null.
disconnect(q, nullptr, nullptr, nullptr); would have pretty catastrophic
consequences as it disconnects everything. Anyone listening for
QObject::destroyed of IconItem for cleanup would no longer get anything.
That could lead to obscure conditions.
ShaderEffectSource watches for the source being destroyed for cleanup
and we have a newly introduced crash with ShaderEffectSource that seems
to come from this patch.
CCBUG: 421170