qt: update widgets availability on wallet selection

Add m_mask_value_action into setWalletActionsEnabled function so it's
only enabled when a wallet is selected. For the transaction history
view check if there's a selected wallet on enableHistoryAction() since
its availability also depends on the mask value checkbox.

src/qt/bitcoingui.cpp

@@ -673,8 +673,10 @@ void BitcoinGUI::setClientModel(ClientModel *_clientModel, interfaces::BlockAndH
 #ifdef ENABLE_WALLET
 void BitcoinGUI::enableHistoryAction(bool privacy)
 {
-    historyAction->setEnabled(!privacy);
-    if (historyAction->isChecked()) gotoOverviewPage();
+    if (walletFrame->currentWalletModel()) {
+        historyAction->setEnabled(!privacy);
+        if (historyAction->isChecked()) gotoOverviewPage();
+    }
 }
 
 void BitcoinGUI::setWalletController(WalletController* wallet_controller, bool show_loading_minimized)
@@ -803,6 +805,7 @@ void BitcoinGUI::setWalletActionsEnabled(bool enabled)
     m_close_wallet_action->setEnabled(enabled);
     m_close_all_wallets_action->setEnabled(enabled);
     m_migrate_wallet_action->setEnabled(enabled);
+    m_mask_values_action->setEnabled(enabled);
 }
 
 void BitcoinGUI::createTrayIcon()