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(!clientModel)
        return;
    if (!isHidden() && !isMinimized() && !GUIUtil::isObscured(this) && fToggleHidden) {
        hide();
    } else {
        GUIUtil::bringToFront(this);
    }
}
void BitcoinGUI::toggleHidden()
{
    showNormalIfMinimized(true);
}
void BitcoinGUI::detectShutdown()
{
    if (m_node.shutdownRequested())
    {
        if(rpcConsole)
            rpcConsole->hide();
        qApp->quit();
    }
}
void BitcoinGUI::showProgress(const QString &title, int nProgress)