Using master (98958c81f5065a5de13699d46995d278ecb6709e) with Qt `5.12.3` (also tested with depends) with multiple wallets available. None are shown in the `Open Wallet ->` menu in the gui. The wallets can be loaded from the console, bitcoin-cli etc.
{
    if (_optionsModel)
    {
        this->optionsModel = _optionsModel;
        
        connect(_optionsModel, &OptionsModel::displayUnitChanged, this, &UnitDisplayStatusBarControl::updateDisplayUnit);
        
        updateDisplayUnit(_optionsModel->getDisplayUnit());
    }
}
void UnitDisplayStatusBarControl::updateDisplayUnit(int newUnits)
{
    setText(BitcoinUnits::longName(newUnits));
}
void UnitDisplayStatusBarControl::onDisplayUnitsClicked(const QPoint& point)
{
    QPoint globalPos = mapToGlobal(point);
    menu->exec(globalPos);
}
void UnitDisplayStatusBarControl::onMenuSelection(QAction* action)
{
    if (action)
    {
        optionsModel->setDisplayUnit(action->data());
    }
}