qt: Persist Mask Values option

The mask values option is memory only. If a user has enabled this
option, it's reasonable to expect that they would want to have it
enabled on the next start.

src/qt/overviewpage.cpp

@@ -173,6 +173,7 @@ void OverviewPage::handleTransactionClicked(const QModelIndex &index)
 void OverviewPage::setPrivacy(bool privacy)
 {
     m_privacy = privacy;
+    clientModel->getOptionsModel()->setOption(OptionsModel::OptionID::MaskValues, privacy);
     const auto& balances = walletModel->getCachedBalance();
     if (balances.balance != -1) {
         setBalance(balances);