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.
std::vector<CRecipient> vecSend;
    
    for (size_t idx = 0; idx < tx.vout.size(); idx++) {
        const CTxOut& txOut = tx.vout[idx];
        CRecipient recipient = {txOut.scriptPubKey, txOut.nValue, setSubtractFeeFromOutputs.count(idx) == 1};
        vecSend.push_back(recipient);
    }
    
    
    LOCK(wallet.cs_wallet);
    
    
    std::map<COutPoint, Coin> coins;
    for (const CTxIn& txin : tx.vin) {
        coins[txin.prevout]; 
    }
    wallet.chain().findCoins(coins);
    for (const CTxIn& txin : tx.vin) {
        const auto& outPoint = txin.prevout;
        if (wallet.IsMine(outPoint)) {
            
            coinControl.Select(outPoint);
        } else if (coins[outPoint].out.IsNull()) {
            error = _("Unable to find UTXO for external input");
            return false;
        } else {
            
            coinControl.SelectExternal(outPoint, coins[outPoint].out);
        }
    }