clang-tidy, qt: Fix modernize-use-default-member-init in headers

See https://clang.llvm.org/extra/clang-tidy/checks/modernize/use-default-member-init.html

src/qt/walletmodel.cpp

@@ -46,10 +46,6 @@ WalletModel::WalletModel(std::unique_ptr<interfaces::Wallet> wallet, ClientModel
     m_client_model(&client_model),
     m_node(client_model.node()),
     optionsModel(client_model.getOptionsModel()),
-    addressTableModel(nullptr),
-    transactionTableModel(nullptr),
-    recentRequestsTableModel(nullptr),
-    cachedEncryptionStatus(Unencrypted),
     timer(new QTimer(this))
 {
     fHaveWatchOnly = m_wallet->haveWatchOnly();