qt: Fix regression in TransactionTableModel

Since #17993 a crash is possible on exit.

Co-authored-by: Russell Yanofsky <[email protected]>

Author: hebasto

src/qt/transactiontablemodel.cpp

@@ -664,7 +664,7 @@ QVariant TransactionTableModel::headerData(int section, Qt::Orientation orientat
 QModelIndex TransactionTableModel::index(int row, int column, const QModelIndex &parent) const
 {
     Q_UNUSED(parent);
-    TransactionRecord* data = priv->index(walletModel->wallet(), walletModel->clientModel().getBestBlockHash(), row);
+    TransactionRecord* data = priv->index(walletModel->wallet(), walletModel->getLastBlockProcessed(), row);
     if(data)
     {
         return createIndex(row, column, data);

src/qt/walletmodel.cpp

@@ -87,7 +87,7 @@ void WalletModel::pollBalanceChanged()
 {
     // Avoid recomputing wallet balances unless a TransactionChanged or
     // BlockTip notification was received.
-    if (!fForceCheckBalanceChanged && m_cached_last_update_tip == m_client_model->getBestBlockHash()) return;
+    if (!fForceCheckBalanceChanged && m_cached_last_update_tip == getLastBlockProcessed()) return;
 
     // Try to get balances and return early if locks can't be acquired. This
     // avoids the GUI from getting stuck on periodical polls if the core is
@@ -588,3 +588,8 @@ void WalletModel::refresh(bool pk_hash_only)
 {
     addressTableModel = new AddressTableModel(this, pk_hash_only);
 }
+
+uint256 WalletModel::getLastBlockProcessed()
+{
+    return m_client_model ? m_client_model->getBestBlockHash() : uint256{};
+}

src/qt/walletmodel.h

@@ -155,6 +155,9 @@ class WalletModel : public QObject
     AddressTableModel* getAddressTableModel() const { return addressTableModel; }
 
     void refresh(bool pk_hash_only = false);
+
+    uint256 getLastBlockProcessed();
+
 private:
     std::unique_ptr<interfaces::Wallet> m_wallet;
     std::unique_ptr<interfaces::Handler> m_handler_unload;