A user reported to me that they are unable to create a PSBT with a legacy watchonly wallet when they use the GUI. They get an error "The amount exceeds your balance".

I think the issue is that the GUI will retrieve the wallet's balance via `AvailableCoins` before calling `CreateTransaction`. This call to `AvailableCoins` is resulting in fewer coins being returned with recent changes to how `AvailableCoins` works, particularly with additional filtering of spendable coins and preset coins.

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Note that this does not effect descriptor wallets. A workaround for this issue is to switch to using descriptor wallets. An existing legacy wallet can be turned into a descriptor wallet using the `migratewallet` RPC. However many watchonly legacy wallets are likely the result of importing descriptors via `importmulti`. For such wallets, I recommend creating a new descriptor wallet and re-importing the descriptors.
#include <node/interface_ui.h>
#include <psbt.h>
#include <util/system.h> 
#include <util/translation.h>
#include <wallet/coincontrol.h>
#include <wallet/wallet.h> 
#include <stdint.h>
#include <functional>
#include <QDebug>
#include <QMessageBox>
#include <QSet>
#include <QTimer>
using wallet::CCoinControl;
using wallet::CRecipient;
using wallet::DEFAULT_DISABLE_WALLET;
WalletModel::WalletModel(std::unique_ptr<interfaces::Wallet> wallet, ClientModel& client_model, const PlatformStyle *platformStyle, QObject *parent) :
    QObject(parent),
    m_wallet(std::move(wallet)),
    m_client_model(&client_model),
    m_node(client_model.node()),
    optionsModel(client_model.getOptionsModel()),
    timer(new QTimer(this))
{
    fHaveWatchOnly = m_wallet->haveWatchOnly();
    addressTableModel = new AddressTableModel(this);
    transactionTableModel = new TransactionTableModel(platformStyle, this);
    recentRequestsTableModel = new RecentRequestsTableModel(this);
    subscribeToCoreSignals();
}
WalletModel::~WalletModel()