Merge bitcoin-core/gui#8: Fix regression in TransactionTableModel

d906aaa117e337fc70575beecc0d6da314f57385 qt: Fix regression in TransactionTableModel (Hennadii Stepanov)

Pull request description:

  Since https://github.com/bitcoin/bitcoin/pull/17993 a crash is possible on exit.

  Steps to reproduce:
  - precondition: the old chain
  - start `bitcoin-qt`
  - wait until sync
  - on main window: Menu -> File -> Quit
  - crash

  This PR is based on ryanofsky's [suggestion](https://github.com/bitcoin-core/gui/issues/7#issuecomment-646639251).

  Fixes #7.

ACKs for top commit:
  promag:
    Code review ACK d906aaa117e337fc70575beecc0d6da314f57385.
  ryanofsky:
    Code review ACK d906aaa117e337fc70575beecc0d6da314f57385. Only changes are squashing, adding assert and adding const
  vasild:
    ACK d906aaa1

Tree-SHA512: 99a475fd90dff50407a58537fdc6099a2a074018e9078452bf86defc1a4b9e546aa94f916d242355900b21638c6cfef845598a5282661a9343556c4514eb155f

4 files changed, 12 insertions, 3 deletions

diff --git a/src/qt/transactionrecord.cpp b/src/qt/transactionrecord.cpp
index 52007ef350..632a18de5c 100644
--- a/src/qt/transactionrecord.cpp
+++ b/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;
 }
 
diff --git a/src/qt/transactiontablemodel.cpp b/src/qt/transactiontablemodel.cpp
index 327a489488..22ba5187bb 100644
--- a/src/qt/transactiontablemodel.cpp
+++ b/src/qt/transactiontablemodel.cpp
@@ -192,7 +192,7 @@ public:
             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);
diff --git a/src/qt/walletmodel.cpp b/src/qt/walletmodel.cpp
index 72c75f7be0..1143969352 100644
--- a/src/qt/walletmodel.cpp
+++ b/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{};
+}
diff --git a/src/qt/walletmodel.h b/src/qt/walletmodel.h
index 38e8a14556..fd52db2da3 100644
--- a/src/qt/walletmodel.h
+++ b/src/qt/walletmodel.h
@@ -155,6 +155,9 @@ public:
     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;