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.
fNewRecipientAllowed = true;
        return;
    }
    bool send_failure = false;
    if (retval == QMessageBox::Save) {
        // 
        CMutableTransaction mtx = CMutableTransaction{*(m_current_transaction->getWtx())};
        PartiallySignedTransaction psbtx(mtx);
        bool complete = false;
        // 
        TransactionError err = model->wallet().fillPSBT(SIGHASH_ALL, /*lse, /*ue, /*llptr, psbtx, complete);
        assert(!complete);
        assert(err == TransactionError::OK);
        // 
        presentPSBT(psbtx);
    } else {
        // 
        assert(!model->wallet().privateKeysDisabled() || model->wallet().hasExternalSigner());
        bool broadcast = true;
        if (model->wallet().hasExternalSigner()) {
            CMutableTransaction mtx = CMutableTransaction{*(m_current_transaction->getWtx())};
            PartiallySignedTransaction psbtx(mtx);
            bool complete = false;
            // 
            // 
            TransactionError err = model->wallet().fillPSBT(SIGHASH_ALL, /*lse, /*ue, /*llptr, psbtx, complete);
            assert(!complete);
            assert(err == TransactionError::OK);
            send_failure = !signWithExternalSigner(psbtx, mtx, complete);
            //