qt: Fix regression in TransactionTableModel

Since bitcoin#17993 a crash is possible on exit.

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

src/qt/transactionrecord.cpp

@@ -234,6 +234,7 @@ void TransactionRecord::updateStatus(const interfaces::WalletTxStatus& wtx, cons
 
 bool TransactionRecord::statusUpdateNeeded(const uint256& block_hash) const
 {
+    assert(!block_hash.IsNull());
     return status.m_cur_block_hash != block_hash || status.needsUpdate;
 }
 

src/qt/transactiontablemodel.cpp

@@ -192,7 +192,7 @@ class TransactionTablePriv
             interfaces::WalletTxStatus wtx;
             int numBlocks;
             int64_t block_time;
-            if (rec->statusUpdateNeeded(cur_block_hash) && wallet.tryGetTxStatus(rec->hash, wtx, numBlocks, block_time)) {
+            if (!cur_block_hash.IsNull() && rec->statusUpdateNeeded(cur_block_hash) && wallet.tryGetTxStatus(rec->hash, wtx, numBlocks, block_time)) {
                 rec->updateStatus(wtx, cur_block_hash, numBlocks, block_time);
             }
             return rec;
@@ -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() const
+{
+    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() const;
+
 private:
     std::unique_ptr<interfaces::Wallet> m_wallet;
     std::unique_ptr<interfaces::Handler> m_handler_unload;