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)
{
    QString strTitle = tr("Bitcoin"); 
    
    int nMBoxIcon = QMessageBox::Information;
    int nNotifyIcon = Notificator::Information;
    QString msgType;
    
    if (!title.isEmpty()) {
        msgType = title;
    }
    else {
        switch (style) {
        case CClientUIInterface::MSG_ERROR:
            msgType = tr("Error");
            break;
        case CClientUIInterface::MSG_WARNING:
            msgType = tr("Warning");
            break;
        case CClientUIInterface::MSG_INFORMATION:
            msgType = tr("Information");
            break;
        default:
            break;
        }