TransactionHistory: fix use-after-free bugs

src/model/TransactionHistoryModel.h

@@ -45,8 +45,7 @@ class TransactionHistoryModel : public QAbstractListModel
 
 public:
     enum TransactionInfoRole {
-        TransactionRole = Qt::UserRole + 1, // for the TransactionInfo object;
-        TransactionDirectionRole,
+        TransactionDirectionRole = Qt::UserRole + 1,
         TransactionPendingRole,
         TransactionFailedRole,
         TransactionAmountRole,
@@ -97,6 +96,9 @@ public:
 signals:
     void transactionHistoryChanged();
 
+private:
+    QVariant parseTransactionInfo(const TransactionInfo &tInfo, int role) const;
+
 private:
     TransactionHistory * m_transactionHistory;
 };