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.
BOOST_CHECK_EQUAL(GetBalance(wallet).m_mine_immature, 50 * COIN);
    }
    
    {
        LOCK(cs_main);
        file_number = newTip->GetBlockPos().nFile;
        Assert(m_node.chainman)->m_blockman.PruneOneBlockFile(file_number);
    }
    UnlinkPrunedFiles({file_number});
    
    {
        CWallet wallet(m_node.chain.get(), "", CreateDummyWalletDatabase());
        {
            LOCK(wallet.cs_wallet);
            LOCK(Assert(m_node.chainman)->GetMutex());
            wallet.SetWalletFlag(WALLET_FLAG_DESCRIPTORS);
            wallet.SetLastBlockProcessed(m_node.chainman->ActiveChain().Height(), m_node.chainman->ActiveChain().Tip()->GetBlockHash());
        }
        AddKey(wallet, coinbaseKey);
        WalletRescanReserver reserver(wallet);
        reserver.reserve();
        CWallet::ScanResult result = wallet.ScanForWalletTransactions(oldTip->GetBlockHash(), oldTip->nHeight, {}, reserver, false, false);
        BOOST_CHECK_EQUAL(result.status, CWallet::ScanResult::FAILURE);
        BOOST_CHECK_EQUAL(result.last_failed_block, newTip->GetBlockHash());
        BOOST_CHECK(result.last_scanned_block.IsNull());
        BOOST_CHECK(!result.last_scanned_height);
        BOOST_CHECK_EQUAL(GetBalance(wallet).m_mine_immature, 0);
    }
}
BOOST_FIXTURE_TEST_CASE(importmulti_rescan, TestChain100Setup)