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(!walletFrame)
        return false;
    return walletFrame->setCurrentWallet(name);
}
bool BitcoinGUI::setCurrentWalletBySelectorIndex(int index)
{
    QString internal_name = m_wallet_selector->itemData(index).toString();
    return setCurrentWallet(internal_name);
}
void BitcoinGUI::removeAllWallets()
{
    if(!walletFrame)
        return;
    setWalletActionsEnabled(false);
    walletFrame->removeAllWallets();
}
#endif 
void BitcoinGUI::setWalletActionsEnabled(bool enabled)