I can reproduce an issue with master; v0.17.1rc1 works fine.

Steps to reproduce:
- `bitcoin-qt -regtest`
- open Console window
- repeat `generatetoaddress 1 AN_ADDRESS` some times until crash

Crash occurs both on wayland and x11.

[debug.log](https://github.com/bitcoin/bitcoin/files/2690776/debug.log)

[wallets.zip](https://github.com/bitcoin/bitcoin/files/2690781/wallets.zip)
{
    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());
    }
}